Answer:
C. If the outlier is included in the data, the box plot would be significantly skewed.
Explanation:
A and D are saying the same thing so the answer could not be one or the other. It is not D because it would change. It is not A because it would change. In this circumstance the mean would increase so it is not B. Therefore you are left with C and it makes sense, because if the data point is added then the mean would change as well as Q1 and Q3.