Are you sure you typed the right question..

In the question you have written "Ëmployment rose......"

Howeverm the the explanation you have written "Employment costs....."

Here is the corrected question:

Employment costs rose 2.8 percent in the 12 months that ended in September, slightly less than they did in the year that ended in the year that ended in the previous quarter.

The answer is A: Correct as is.

However, I answered B: "less than it did". Why is the the word "they" used to modify employment costs when employment costs are not people?? Shouldn't the word "it" be used?

buddy.....here subject is COSTS....obvious that a plural verb is needed