Heres the question...
1. All members of Group IV include all members of Group II
2. All members of Group III include all members of Group I
3. All members of Group IV include all members of Group I
4. All members of Group II include all members of Group I
5. All members of Group III include all members of Group IV

Which of the following statements must be true in order to establish that Group III is the all-embracing group, that is, includes Groups I, II and IV?

A. Statement 1 is a vital piece of information.
B. Statement 2 is a vital piece of information.
C. Statement 3 is a vital piece of information.
D. Statement 4 is a vital piece of information.
E. None of the above statements is a vital piece of information.

OA after some discussion.

sankruth wrote:Heres the question...
1. All members of Group IV include all members of Group II
2. All members of Group III include all members of Group I
3. All members of Group IV include all members of Group I
4. All members of Group II include all members of Group I
5. All members of Group III include all members of Group IV

Which of the following statements must be true in order to establish that Group III is the all-embracing group, that is, includes Groups I, II and IV?

A. Statement 1 is a vital piece of information.
B. Statement 2 is a vital piece of information.
C. Statement 3 is a vital piece of information.
D. Statement 4 is a vital piece of information.
E. None of the above statements is a vital piece of information.

OA after some discussion.

This question makes absolutely no sense at all.

First, there's no GMAT definition of "vital piece of information", so without defining that term, the question is ambigious.

Second, even if we accept that "vital piece of information" means "something that must be true in order to reach the conclusion" (which seems redundant, since they could have simply asked "which of the above statements must be true in order to reach the conclusion that..." and the the choices would simply have been statements 1-4 or 1-5), all 4 statements could be used in different combinations to conclude that group III is all encompassing: 1, 4 and 5; 1, 3 and 5; or 1, 2 and 5.

Based on that analysis, it looks like the answer will be (A) statement I, since we need either statment 2, 3 or 4, so I guess none are "vital" (i.e. if we have one of the others, we don't need that one). However, we need at least one of the three, so together they form a "vital trio" or some such nonesense.

All that said, is statment 1 really "vital". No, because there could be other statements (not listed) that could replace it.

There's no way at all that a question like this would appear on the GMAT, it's far too open to multiple interpretation.

Thanks guys!