请教一道考古题

Marie Bonaparte put up the ransom that the Nazis insisted on if Freud was to be allowed to leave Vienna.

(B) if Freud were allowed

(C) should Freud be allowed

(D) if they will allow Freud

(E) should allowance be made for Freud

求教思路...thanks a lot!!

首先排除D－they缺指代，且时态错；

排除E，表达罗嗦；

排除C，虚拟语气时态错；

排除B，虚拟语气时态错；

我选A，表示过去事件，没有虚拟的必要。