This is not so much about the answers themselves but more about the way a prospective VA answers the question. A capable person, whether he is a virtual assistant or not, would be aware of his own strengths and weaknesses and will be able answer this question without a problem.

But if the applicant believes that he has no weakness, then obviously, you might want to move on to the next candidate. This basically means that that person is not open to growth and change. He might also have problems with accepting accountability or constructive criticisms in case he makes mistakes.