[求助]再问一道。。。

 The British Admiralty and the War Office met in March 1892 to consider a possible Russian
attempt to seize Constantinople and how they would have to act militarily to deal with them.
(A) how they would have to act militarily to deal with them
(B) how to deal with them if military action would be necessary
(C) what would be necessary militarily for dealing with such an event
(D) what military action would be necessary in order to deal with such an event
(E) the necessity of what kind of military action in order to take for dealing with it
and 连接的两部分对称
名词性从句.引导词: whether 不能用if/whether or not
what 干扰项 how
正确答案D

我不太明白，这里的对称，是a possible Russian attempt 和what 引导的从句对称吗？

这里的WHAT是个什么从句呢，从句和名词能平行？赐教了。。。

应该是a possible Russian attempt 和what引导的 military action 对称