请教OG10 90

90. Since 1986, when the Department of Labor began to allow investment officers' fees to be based on how the funds they manage perform, several corporations began paying their investment advisers a small basic fee, with a contract promising higher fees if the managers perform well.

(A)              investment officers’ fees to be based on how the
                funds they manage perform, several corporations began

(B)              investment officers’ fees to be based on the
                performance of the funds they manage,
                several corporations began

(C)             that fees of investment officers be based on how the funds they manage perform, several corporations have begun

(D)             fees of investment officers to be based on the performance of the funds they manage,
                several corporations have begun

(E)
                that investment officers' fees be based on the
                performance of the funds they manage,
                several corporations began

furthermore, in each of these options, they has no referent, since officers is a possessive modifier of fees. 是什么意思啊？谢谢。