Yes, that's true.

Think about it this way: If statement 1 allows you to answer the target question with certainty, and statement 2 provides the same info that statement 1 does, then statement 2 must also be sufficient, which means the answer is D.

Conversely, if statement 1 does NOT allow you to answer the target question with certainty, and statement 2 provides the same info that statement 1 does, then statement 2 must CANNOT be sufficient either. When we combine two identical statements (and each statement is not sufficient), it's still impossible for us to answer the target question.

Example:
Target question: What is the value of positive integer x
Statement 1: (x - 1)(x - 3) = 0
Statement 2: x is a factor of 3
Each statement provides the same information: x = 1 or 3
So, when we COMBINE statements, we don't learn anything new. So, the answer is E
For more on this, please see our free video: https://www.gmatprepnow.com/module/gmat- ... cy?id=1109

Cheers,
Brent