Since 1990 the global economy has grown more than it did during the 10,000 years from the beginning of agriculture to 1950.

A) Since 1990 the global economy has grown more than it did during the 10,000 years from the beginning of agriculture to 1950.
B) Since 1990 the growth of the global economy has been more than that during 10,000 years, from when agriculture began.
C) The growth of the global economy since 1990 exceeds that which had been for 10,000 years from the beginning of agriculture.
D) The growth of the global economy since 1990 exceeds what it has been for 10,000 years, from when agriculture began
E) The growth of the global economy since 1990 exceeds what it did for the 10,000 years from the beginning of agriculture.

I put answer E but the answer is A. Why is it A????

The last part "what it did for the 10,000 years from the beginning of agriculture" is awkward to the point that it obscures the meaning of the sentence. Should use growth... exceeds what it was, not what it did. In addition, we have lost the fact that it is from the beginning of agriculture to 1950.

What's wrong with D?

Just realized something after I posted my previous message.

Is the issue with D "has been?" Can't be in present perfect because the growth rate from the start of agriculture to 1950 is no longer continuing?

Stacey: I'm assuming that 'to 1950' wasn't supposed to be in ANY of the answer choices, and that putting it into choice A was an innocent mistake. (Otherwise, the answer to this problem would just be way too obvious.)

Yeah, you can't use the present perfect if the time interval is over. If the trend continues into the present day, then the present perfect is appropriate.

Even if that were fixed, choice D still suffers from fatal wordiness / lack of concision, especially in comparison to the correct choice.

That's a lot of question marks in the original post.

How about B?
Some people said that "from when" is not right.
Can "that" in choice B represents "the growth of the global economy"? Or "that" could only refer to one noun?
Thanks in advance.

you can't use 'that' in this sort of construction, because constructions using 'that of' (or other preposition after 'that') must have EXACTLY parallel structures. in other words, if the second half says 'that during 10,000 years', then the preceding half must say 'the growth of ___ during something else' (or some other time preposition, such as before or after, in place of during).

there's nothing ungrammatical about 'from when', because the clause starting with 'when' is a perfectly legitimate noun clause (i.e., 'when agriculture began' serves as a noun. however:
- it's possible that the gmat does consider such constructions wrong; the only way to tell is to see if they say so in any official answer choices
- regardless of where the gmat stands on the issue, 'the beginning of agriculture' is unquestionably better than 'when agriculture began' (i.e., an actual noun is almost always superior to a circuitous noun clause, when possible)

What was wrong with E

E) The growth of the global economy since 1990 exceeds what it did for the 10,000 years from the beginning of agriculture.

'what it did' doesn't make any sense:
* the growth didn't 'do' anything
* there's no other verb to which 'did' could logically be parallel to complete the comparison

Hi Ron,

I assume that the rule applies to "those+preposition" in a comparison sentence (such as an "as...as" sentence and a "than" sentence)

I have read through all OG 10 SC questions, and it seems like that 2 of them are exceptions:
19. In addition to having more protein than wheat does, rice has protein of higher quality than that in wheat, with more of the amino acids essential to the human diet.
112. Domestic automobile manufacturers have invested millions of dollars in research to develop cars even more gasoline-efficient than those at present on the road.
(I know that I am not supposed to post OG questions because of the copyright issue; hope that it is okay to post without posting the full questions; otherwise, please delete my questions and leave the question #s so that other can refer to their OG books)

I believe that the "exactly parallal structures" refer to a pair of prepositional phrases serving the similar function. If my understanding is correct, then #19 is an exception to your rule.
In #112 "cars" isn't followed by preposition....

Did I interpret your rule incorrectly?
Thanks in advance.

wow. whoever you are, we should hire you to do research for us.

in #112, "at present" isn't part of the parallel construction; it's an idiomatic expression with the same meaning as the word "now". i.e., you could write this as ...than those now on the road, and the meaning would stick. so that is a non-issue.

#19 is interesting. there's still LOGICAL parallelism - you have the protein contained in rice, and you have the protein contained in wheat - but the GRAMMATICAL parallelism isn't lock-step: you have "rice has protein" vs. "that in wheat". in other words, while both halves refer to the protein contained in a particular type of food, they do so in slightly different ways.
the lesson here is that we shouldn't complain, but, rather, we should learn: if the logical parallelism is absolutely clear, then the gmat will tolerate slight anomalies from the ideal of exact grammatical parallelism.

Thanks Ron.
The more comparison SCs I work on, the more confused I am about GAMC's grammar rules.

Isn't 'it' in choice D, E ambiguous?
'it' could refer to either 'growth' or 'global economy'? Thanks.

Yes, correct. That is *another* reason to eliminate D, E (in addition to those discussed above). Nicely done.