问两道语法题 进来的麻烦解答下~~~

1.Once they had seen the report from the medical examiner, the investigators did not doubt whether the body recovered from the rier was the man who had attempted to escape from the state prison.
(A)did not doubt whether the body recovered from the rier was
(B)have no doubt whether the body recovered from the river was
(C)had not doubted that the body recovered from the river was
(D)have no doubt whether the body recovered from the river was that of
(E)had no doubt that the body recovered from the river was that of
这题问的跟答案不太有关系 就想知道这句话是once 引导的条件从句么 最好能详细说下the medical examiner, the investigators之间的关系 现在看到the medical examiner后面那个逗号就想加and

2The capital of Bosnia-Herzegovina, Sarajevo's population on the eve of the First World War was 51,919.
(A)Bosnia-Herzegovina, Sarajevo's population
(B)Bosnia-Herzegovina is Sarajevo, whose population
(C)Bosnia-Herzegovina is Sarajevo, with a population
(D)Bosnia-Herzegovina, Sarajevo having apopulation that
(E)Bosnia-Herzegovina, the population of Sarajevo
问下D这个答案是定语从句形式么 was是从句的谓语动词么 所以主语缺少谓语动词。
小弟不才 虚心求教饿 感觉问题都好弱 望牛牛们不辞辛苦开恩解答