og244时态问题

244. Like their male counterparts, women scientists are above average in terms of intelligence and creativity, but unlike men of science, their female counterparts have had to work against the grain of occupational stereotyping to enter a "man's world."

(A)              their female counterparts have had to work

(B)              their problem is working

(C)             one thing they have had to do is work

(D)             the handicap women of science have had is
                    to work

(E)              women of science have had to work

这个题选E没有问题，从比较结构来说只有E符合，但是E的时态我不太明白，为什么用have had 呢？请各位看看！