The correct option is B I'm not sure. I can't find them on the rack. But let me check in the storeroom.
Option B: This does not seem like a suitable reply. As it's given in the question, the person's (Krishna's) size is seven. So, offering shoes with size six isn't a suitable thing to do. Hence B is incorrect.
Option C: This reply, too, isn't appropriate. Offering a customer (Krishna) a size bigger isn't a desirable thing to do.
Hence option C is incorrect.
Since both B and C are incorrect, option D is also not the right answer.
Option A: This is the most fitting reply, as the sales man offers a proper solution, that he'd go and check in the storeroom if Krishna's size is available.
Hence, A is correct.