The median is most likely to be meaningful:

• The average is distorted by the single very high salary, and so is not a good measure of the 'typical' salary

• The mode is not meaningful. Two salaries are the same, but this could be either coincidence or two employees on the same grade

• The median is the best measure for this example

Note:

• the data set is unrealistically small, but I just want to illustrate the point

• the answer is the most likely, I can think of some purposes for which the average might be most useful