问一个句子，困惑好久了...

jimmyhou520

12. Affording strategic proximity to the Strait of Gibraltar， Morocco was also of interest to the French throughout the first half of the twentieth century because they assumed that if they did not hold it， their grip on Algeria was always insecure.
（A）if they did not hold it， their grip in Algeria was always insecure
（B）without it their grip on Algeria would never be secure （正确）
(C) their grip on Algeria was not ever secure if they did not hold it
(D) without that， they could never be secure about their grip on Algeria (that不能单独接在介词后，错误)
(E) never would their grip on Algeria be secure if they did not hold it （倒装语序改变句子语气，错误）


对于AC答案，白勇的语法书上以不符合虚拟语气唯由判错了....但为什么这两句不能够被看成是IF引导的条件状语从句呢...？


条件状语从句中 从句用一般现在时表将来，此时主句可以用将来时...那主句可以用一般现在时么？
同时，条件状语从句中，从句也可以用一般过去时，那么这时主句应该用什么时态？不可以用一般过去时么？ 还是必须要用过去将来时，那就和虚拟语气一样了...

bitieming

就是IF引导的条件状语从句中的虚拟语气吧，A中应该是would be always inseure才符合虚拟语气，C中was not ever 的表述awkward。
条件状语从句主语可以不是将来时，例句：
I can tell you the truth if you promise to keep the secret.
从句用过去式一般就虚拟语气啦，例句：
He would not be against us in the meeting if we asked for his advice in advance.

jimmyhou520

就是IF引导的条件状语从句中的虚拟语气吧，A中应该是would be always inseure才符合虚拟语气，C中was not ever 的表述awkward。
条件状语从句主语可以不是将来时，例句：
I can tell you the truth if you promise to keep the secret.
从句用过去式一般就虚拟语气啦，例句：
He would not be against us in the meeting if we asked for his advice in advance.

-- by 会员 bitieming (2011/7/26 19:29:42)

啊！谢谢大大！豁然开朗了...