PREP1-31 a two-year low level& the lowest level in tow years

According to some economists, the July decrease in unemployment so that it was the lowest in two years suggests that the gradual improvement in the job market is continuing.   E

(A) so that it was the lowest in two years

(B) so that it was the lowest two-year rate

(C) to what would be the lowest in two years

(D) to a two-year low level

(E) to the
                lowest level in two years
            

D 哪里错了啊？

给你两个解释

1 不符合英语语言习惯 这个没有什么道理可讲

2 可以被错误地理解为 一个持续了两年的低水平 因此表意模糊