Both the caribou and the reindeer belong to the species Rangifer tarandus, but after 7,000 years of domestication in Eurasia, reindeer have developed a tendency to circle in tight groups, while caribou tend to spread far and wide.

(A) belong to the species Rangifer tarandus, but after 7,000 years of domestication in Eurasia, reindeer have developed a tendency to circle in tight groups, while caribou tend
(B) belong to the same species, Rangifer tarandus, but about 7,000 years of domestication in Eurasia have developed reindeer's tendency to circle in tight groups, which is different from caribou that tend
(C) belong to the species Rangifer tarandus, but being domesticated in Eurasia for about 7,000 years has developed reindeer's tendency to circle in tight groups, and that is different from caribou tending
(D) are the same species, Rangifer tarandus, but about 7,000 years of domestication in Eurasia have developed reindeer's tendency to circle in tight groups, while the tendency is for caribou
(E) are the same species, Rangifer tarandus, but being domesticated in Eurasia for about 7,000 years has developed the reindeer's tendency to circle in tight groups, which differs from caribou tending
OA is A. Could you tell me the structure of A?

i'm not sure exactly what you mean by 'the structure of' choice a, but i'll give it a shot. before that discussion, though, i'll tell you a bit about what's wrong with the other answer choices.

ALL of b, c, d, e (wow):
- unacceptable chance of meaning in the wording '7000 years ... have developed reindeer's tendency'. the implication is that the passage of time itself has somehow developed the tendency. choice a retains the proper, sensible meaning: after all that time, reindeer have somehow developed a tendency, although the exact mechanism of development remains unspecified.

choice e:
- ARE the same species isn't acceptable: from the context, the correct expression is that the animals _belong_ to the species. if you're in doubt about this, remember that the gmat is very exacting about using copulative verbs (verbs that say that this IS that), so try to use the non-copulative verbs (such as 'belong to' here) when possible.
- the use of the relative pronoun 'which' is incorrect: relative pronouns modify the noun directly preceding, meaning in this case that 'which' must modify 'tight groups'.
- even if you let 'which' slide, there's bad parallelism between tendency and caribou (faulty comparison).

choice d:
- same issue with ARE vs. 'belong to'
- idiomatic usage problem with 'the tendency is for...': proper usage is 'X has a tendency to VERB'

choice c:
- can't use the pointing word 'that' (or 'this' or 'those' or 'these') by itself. you can only use these words as adjectives (that reason, these people) or as pronouns in constructions like 'that of...'
- faulty parallelism between tendency and caribou
- can't say 'caribou tending...' (you'd need a possessive form like caribou's)

choice b:
- one could say there's a bit of redundancy in the 'same' wording. i wouldn't have noticed that redundancy if this choice showed up in isolation (as a sentence in a student paper, for example), but it's evident upon comparison to choices a and c. (compare the answer choices to each other as much as possible! it's much easier to decide whether x is better than y than to decide whether x is 'good' by itself!)
- same problem as choice e with the relative pronoun 'which'
- faulty comparison between tendency and caribou
- 'caribou that tend...' uses an essential modifier, which means that we're restricting the discussion to only those caribou that have the given tendency. (if there were a comma and a different relative pronoun - caribou, which tend to... - then that construction would refer to all caribou)

--

'structure' of choice a:
- the overall structure is 2 independent clauses (each a perfectly good sentence in its own right) connected by the conjunction 'but':
Both the caribou and the reindeer belong to the species Rangifer tarandus
but
after 7,000 years of domestication in Eurasia, reindeer have developed a tendency to circle in tight groups, while caribou tend to spread far and wide.

- the first clause is concise (it doesn't waste words on the construction 'same species')
- the second clause starts with an adverb phrase (it's a time phrase), which can modify the following clause in its entirety
- parallelism is good: reindeer do that, while caribou do this
- all verbs are in present tense

thanks man.

so wait, is there a question here?
i don't see one - it looks as though you're just recapping your knowledge - but i want to make sure.

Ron

in the right answer :

but after 7,000 years of domestication in Eurasia, reindeer have developed a tendency to circle in tight groups, while caribou tend to spread far and wide.

the bold face thense is in Present perfect and Simple present.

Do we need in case of parallelinsm all verbs in the same catagory

It's a good question. There are cases where you can have the Present Tense and the Present Perfect Tense function as parallel, without a problem. Part of the reason for this is due to the meaning of the verbs in play. For example, you can't express the idea that the reindeer "have developed" something without using the present perfect. (You could change the words that you use entirely. But you can't say "reindeer develop," because that has the wrong meaning.) This development happened in the past, but it's expressed in the present because it is important now. It is okay to then match this to a verb that is in the simple present tense.

The present perfect is weird in this respect, but this can be seen on some OG problems as well. Basically, know how to use each of the tenses, but don't stress too much about a seemingly non-parallel construction between the present perfect and the simple present.

could someone pls explain why reindeer and caribou both use "have' and "tend", not "has" and "tends"? is it because they both refer to the species?

Both the caribou and the reindeer belong to the species Rangifer tarandus, but after 7,000 years of domestication in Eurasia, reindeer have developed a tendency to circle in tight groups, while caribou tend to spread far and wide.

thanks!

"reindeer" and "caribou" - like "fish" - can be either singular or plural. in this case, they must be plural, as can be seen from the lack of articles.
i.e., if "reindeer" were singular, it couldn't just be "reindeer" - it would have to be "THE reindeer" or "A reindeer" (or something else, like "north america's reindeer", etc.)

1# wait, dose the rule just apply to "reindeer" ,"caribou" , "fish" and the like or it applies to other animal such as frog, lion, and bird? i don't know the differences! Ron, can you explain?
2# 7,000 years of domestication in Eurasia have----is 'plural' have OK?
Ron,you said when subject is X years/times/tons/kilograms, Verb is singlar. what about 3 kilograms of apples or 3 kilograms of water, sigular or plural?

_________________
stephen

there's no "explanation". unfortunately, this is TOTALLY AND COMPLETELY idiomatic, on a case-by-case basis.

if you are really, really interested (and i mean really interested), there is a fairly complete list here:
http://www.anapsid.org/beastly.html
just look at the first two columns.

idioms suck, i know. sorry.



you are correct; it should be "7000 years HAS". it would only be "have" if we were emphasizing the individual years; we're clearly not doing that.

*** WARNING: THIS IS WAY BEYOND THE SCOPE OF THE EXAM: ***
some units of measure can go either way, depending on what you are trying to emphasize.
* if you are emphasizing the units themselves, one at a time, then you use the plural;
* if you are emphasizing the collective quantity as a single entity, then you use the singular.
e.g.
1000 words is a typical length for a high-school essay. --> singular, since we are emphasizing the length of the paper (the measure of a single entity). we are not emphasizing the individual nature of the words.
1000 different words are in the vocabulary book. --> plural, since we are emphasizing the individually different words.
*** END OF TANGENT ***

i think that the gmat will altogether avoid testing this particular nuance.
we've seen it once, but it was in the non-underlined portion of the sentence. since the gmat tests sentences about quantities, numbers, etc. ALL THE TIME, we'd probably have seen this by now if they were going to test it.)

i like warning. so kilograms of apples definitelty are plural, but 3 kilograms of water...depending on concext.

_________________
stephen