Be动词省略问题！！！！

xiaobaibai92112

103. Inuits of the Bering Sea were in isolation from contactwith Europeans longer than Aleuts or Inuits of theNorth Pacifi c and northern Alaska.
(A) in isolation from contact with Europeans longerthan
(B) isolated from contact with Europeans longer than
(C) in isolation from contact with Europeans longerthan were
(D) isolated from contact with Europeans longerthan were
(E) in isolation and without contacts with Europeanslonger than
这道题答案为D，我知道因为主句出现了宾语，为了防止ambiguous，than 之后得加相同的动词，但是不是说Be动词或者become可以省略吗？？？