The correct answer is A.
The second part of this sentence, "[apples' smell] does not come from their grains", must be true according to the third fact. The first part, "Apples may smell", is a bit different, as it is written in a suggestive manner. It cannot be 'false' as long as it does not contradict any of the facts above, which it does not.
Let's go over the remaining answer choices:
Answer choice B – since we are not told anything regarding the smell of apples, we cannot say whether this is true or false.
Answer choice C is eliminated for the same reasoning, as we know nothing about the colour of onions. It is important to remember that we are supposed to answer the question solely on the basis of the information given to us in the facts, regardless of any additional knowledge we might have about onions from the real worldץ
Answer choice D – the fourth fact explicitly states that David does not usually mind strong smells. The only occasion where he would mind them is if he were running a fever. There is no specific exception for onions, which makes this a false statement.
Answer choice E – this statement is neither supported nor contradicted by any of the facts above, so we cannot say whether or not it is true.