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 previous quarter.
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 previous quarter.
A.less than they did
B.less than it did
C.less than they were
D.lower than
E.lower than they were 答案为什么是A,不是B呢 主语是employment,不是应该用单数吗?谢谢啦。。