kthor
I haven't seen this case, but would there ever be a DS question that involves a statement leading to an undefined answer? If you can conclude that the answer is undefined as a result of that statement, would that statement count as sufficient?
Basic example:
What is the value of x?
Statement 1. \(\frac{5}{0}=x\)
Is statement 1. sufficient because you know the answer is "undefined"?
kthorYou will never spot such scenario in GMAT.
GMAT DS questions will not lead you to examples such as you have shown in the post.
For Yes/No DS questions you will always find statments leading to either YES or NO or Both Cases.
For Value based DS questions you will have statements that will answer in either a single value or multiple possibilities for values of a variable.
If by any chance you have "undefined" scenario to arise in your answer, please follow the Question stem, GMAT you surely provide you by some means any details that will help you to eliminate that choice.
Hope this helps