请看下面的题目：

If we __________ 200 years old，we __________ everything.

A. were to be，could change                                                 B. had been，changed

C. were，would have changed                                    D. should be，changed

此题应选A。该题考查与将来事实相反的虚拟语气，此时的主句谓语通常用would(should，could，might)＋动词原形，而从句谓语可能有以下几种情况：

1. 从句谓语用过去式：

If your father knew this，he would be angry. 要是你父亲知道了，他会生气的。

If it rained tomorrow，the sports meet would beput off. 要是明天下雨，运动会就推迟。

2. 从句谓语用should+动词原形(通常指可能性极小的事情，一般译为“万一”)：

If it should rain，the crops would be saved. 要是有雨，这庄稼还有救。

此类句型的主句谓语有时可以用祈使句甚至将来时态：

If it should rain tomorrow，don’t expect me. 万一明天下雨，就不要等我了。

If I should be free tomorrow，I will come. 万一我明天有空，我就来。

3. 从句谓语用were to+动词原形 (通常指可能性极小可或近乎不可能，有时指出乎意料)：

If the sun were to rise in the west，my love for you would not change. 即使太阳从西边出，我对你的爱也不会变。