请问这题如何判断是主语比较还是状语比较?

龍之哀伤

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

请问这题如何判断是主语比较还是状语比较?
看了<<比较之庖丁解牛>>再做这题糊涂了....

tina2012

high-low用以形容指标等等，costs显然是不适用的，使用less-more来形容，然后再看看单复数就可以选了吧

qiyueliuhuo

第一步：用low 而不是less
第二步：对于E选项应该是lower than they did ,而不是they were， 由于是状语比较，所以they did 也可以省略