lunarpower wrote:1000sc is known for not being the world's greatest source. proceed with caution.

(a) is correct, except possibly in its use of "advocate". i THINK that "advocate that..." is unidiomatic, although i'm not sure enough to declare that this is a fact.
if you replace "advocated" with a word that is definitely idiomatic in that sort of construction, such as "proposed", then everything in (a) is grammatical, idiomatic, and correct in every other way.


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(d) and (e) can be eliminated immediately, since "black's" is a singular construction, i.e., referring to one "Black".

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(b) is wrong because it changes the meaning of the sentence. if you say "the african land symbolizing...", then "symbolizing..." is an essential modifier. the implication is that only SOME african land symbolizes blah blah blah, and that's the land we're talking about.

analogy:
the award is given to students maintaining a grade-point average higher than 3.5.
obviously, this does not imply that all students are maintaining a GPA higher than 3.5; it just says that the award will be given to those students who ARE maintaining such a GPA.

same deal with (b), which is why (b) is wrong.

(c) is wrong because it lacks a comma before the first "which", and because the second "which" should be "that".
the gmat NEVER uses "which" (or "to which" or "from which" etc) without a comma immediately preceding.

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any questions about things in choice (a), feel free to ask.

lunarpower wrote:

what i want to know is in place of "-ing form" if there would be "that" as in choice (a) ...then the modifier refers to whole african land.

But "that" is an essential modifier if it refers to whole land its not an essential info.

Well... no.
If that were non-essential, then you could eliminate it without any loss of specificity.
If you try to eliminate that modifier, then you're left saying that Africa is just "the land". That's nonsense, of course; the sentence has to say that Africa is the land that symbolized xxxxx.