A problem about ADT table in Java

Question:
(a) Based on the following scenario, describe one advantage and one disadvantage of each implementation of the ADT Table (using a binary search tree, ordered vector, or unordered vector). (Note that there is certainly more than one acceptable answer for this question.)
"Consider an implementation of the University of Waterloo staff telephone directory system as a dictionary. Given the high turnover of university staff and the unreliability of the telephone system, the addition and removal of persons to the dictionary is quite frequent and needs only occasional retrievals."

(b) Based on your analysis, what would be the most appropriate implementation of the three (a binary search tree, ordered vector, or unordered vector) for the given scenario? Explain your answer.  

The original course website where the problem comes from is here, I think it will be helpful if you take a look at it first: www.student.math.uwaterloo.ca/~cs134