[quote="AbdurRakib"]Between 14,000 and 8,000 b.c. the ice cap that covered northern Asia, Europe, and America
began to melt, uncovering vast new areas that were to be occupied by migrating peoples moving northward.
A. began to melt, uncovering vast new areas that were to be occupied
B. began melting, to uncover vast new areas to be occupied
C. began, by melting, to uncover vast new areas for occupation
D. began, after melting, uncovering vast new areas which are to be occupied
E. would begin to uncover, through melting, vast new areas for occupation
on GMAT SC, meaning relation between two verbs is tested frequently. this question is one example for that.
the intended meaning here is that the melting and uncovering are not separate and , of course, happen at the same time .this meaning relation is shown by comma+doing as in choice A.
choice B
"to uncover" dose not show that melting and uncovering happen at the same time. even "to uncover" show a future action . we do not even know wheather this future action happen. B is gone
choice C.
with the same thinking, "by melting" dose not shows that melting and uncovering happen at the same time. I go to us for mba by learning gmat. in this sentence, learning happen before going. in our question, in choice C, melting can happen before uncovering and this relation is ambiguous.
choice D
with the same thinging , melting happen before uncovering. this is clearly wrong.
choice E
we are not clear melting and uncovering happen at the same time clearly wrong.
comma+doing show an action NOT SEPARATE from the main action. this is tested with "and do" which show a action SEPARATE from main action.
"to do" show a future , non factual action, or at least an action which is not simultaneous with the main action
"would do" and "were to do" show a future action.
the main point here is
ACTION NOT SEPARATE FROM MAIN ACTION
is tested in comparision with
"to do" which is at least separate from the main action , which could be a future action or an factual action which happen after the main verb.
"by doing" show a separate action which could be not simultaneous with the main action. " I learn english by reading english books in evenings" show that "reading" is separate and not simultaneous with "learn".
I will come bank for "by doing" because I see i can know more about it.