Hi Ankitaverma,

In DS questions, it's important to pay attention to every piece of information that you're given.

We're told that A + B = 200 and A < B. With these two pieces of information, we know that B > 100 and A < 100.

We're asked if A + B > C + D? With the first piece of information, we can rewrite the question as...

Is 200 > C + D? This is a YES/NO question.

Fact 1: C + D < 200

This data allows us to easily answer the question (and the answer is ALWAYS YES).
Fact 1 is SUFFICIENT.

Fact 2: B + C + D = 300

At first glance, this might appear insufficient, but remember the information given in the prompt (B > 100). With THAT info, C + D must be less than 200, so the answer to the question is ALWAYS YES.
Fact 2 is SUFFICIENT.

Final Answer: D

GMAT assassins aren't born, they're made,
Rich