求助：VERBAL 2ND 81题，指代问题

81.        Since1986, when the Department of Labor began to allow investment officers' feesto be based on how the funds they manage perform, several corporations began paying their investment advisers a small basic fee, with a contract promising higherfees if the managers perform well.

(B)         investment officers' fees to be based on the performance of the funds they manage, severalcorporations 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

NOTES:

“Since 1986” indicates action begun in the past anscontinuing into the present, and the form of the verb must show the continuity,as the present perfect tense does: since 1986, corporations “have begun”. In the original sentence, the pronoun “they” lacks a clear referent. While “they”should refer unambiguously to “investment officers” , grammatically its referent is somewhat unclear because “investment officers’ ” is a possessive modifying “fees”, and the plural noun “fees” intervenes between “officers’ ”and the pronoun.