Because the question stem says "properly drawn," we know that this is a strengthen w/ sufficient assumption question. Our goal must be to guarantee the conclusion.
The gap in the argument here is this: "Why can't someone be motivated by both a desire for praise and a desire to help others?" Just because they are primarily motivated by praise, it does not mean that helping others can't motivate them as well.
Answer choice A fixes this gap, leading directly to the conclusion.
My guess is that you treated answer choice E as if this were a strengthen w/ necessary premise question. In that case, it would be the correct answer! If the consequences matter instead of the motives, then the whole argument falls apart. However, it does not resolve the gap in argument, nor does it guarantee the conclusion.
