Hi,
I always have big confusion while working with these two tenses."present perfect" and "present perfect continuous" tense.
Though I had read nothing about present perfect continuous in MGMAT SC guide.I have few queries regarding its usage.
1) Is the concept of present perfect continuous ever get tested in GMAT?
2) If yes what is the exact difference in terms of its usage from present perfect tense.
3)In SC guide at chapter 7) it has been mentioned that present perfect should be used with "since".shall we accept it as 100% rule for every "since" we see in any of the sentence.
I also digged a bit at google and found that ideally since should be used with "present perfect continuous" tense and not with "present perfect"(http://www.ego4u.com/en/cram-up/grammar ... -preperpro).
which one I should take as a rule ? please clarify.

Thanks

Present perfect continuous is generally used to describe actions or states of being that are both ongoing and uninterrupted (i.e. continuous). It sometimes refers to an action that has just ended. It is also often paired with measurements of time.

"I have been waiting for you to respond to my post."
"He has been working in the garden all day."
"The boss is mad at him because he has been missing so much work."

Either the present perfect or the present perfect continuous can be used with "since," depending on context. The example in Ch. 7 is "Since 1987." Thus:

"Since 1987, he has not invested in the stock market." (Note that here, as in many such sentences, we could also place "since 1987" at the end of the sentence.)

"Since the accident, he has gone to church more often."
OR
"Since the accident, he has been going to church more often."

Here, "he has been going to church" implies a habitual and repeated action. Compare this to "He has gone to church more often." This implies a less continuous level of activity. Perhaps he is done going to church, but overall his attendance has increased.

Note that this is different from the use of "since" to mean "because." "Since you have been working so hard, you can go home early."

I can't say that I have seen this tested specifically on the GMAT, but it can't hurt, right?

_________________
Dmitry Farber
Manhattan GMAT Instructor

"Present perfect continuous is generally used to describe actions or states of being that are both ongoing and uninterrupted (i.e. continuous). It sometimes refers to an action that has just ended. It is also often paired with measurements of time."

If this is the present perfect continues explanation then how it is different from "present perfect" described in Ch.7 where it states that "the present perfect indicates either continued action or continued effect of a completed action".

How this continued action is different from ongoingh action defined for present perfect continuous.

although you probably don't need to worry too much about this one for the GMAT, the difference between continuous and ongoing can be summarized by this example:

"he has missed work lately"
(he was absent once or twice recently)

"he has been missing work lately"
(he is absent quite a bit of the time recently)

this is often a judgment call and not always clear from context, which is why you won't likely be asked to make a distinction between these two options on the GMAT..

_________________
Tim Sanders
Manhattan GMAT Instructor