If I hadn’t stood under the ladder to catch you when you fell, you ______ now.

A. wouldn’t be smiling                            B. couldn’t have smiled

C. won’t smile                                          D. didn’t smile                         

 (1999年1月四级)

你掉下来时，如不是我在梯子下面把你接住，恐怕你就不是现在这个样了。答案A

在非真实条件句中，有时从句的动词所表示的动作和主句的动词所表示的动作并不同时发生，这样的条件句中使用的虚拟式称为混合虚拟式或称为错综时间条件句。此时，动词的形式要根据表示的时间来调整。而且一般有明确的时间状语如now, then, tomorrow等提示这种差异。

【例句】

I should have brought the box of books myself if it were not heavy. 如果书箱不是这样的沉重，我自己就把它带来了。(从句用一般时，表示客观情况，主句用了完成时，表示过去没有做的动作)

If I had taken my raincoat when I came out this morning, I would not be wet now.

(从句虚拟过去，主句虚拟现在)

If I were you, I wouldn’t have missed the film last night. (从句虚拟现在，主句虚拟过去)

If Tom intended to start out this morning, he would have got everything ready last night. (从句虚拟将来，主句虚拟过去)

If he had taken my advice, he would be a scientist now. (从句虚拟过去，主句虚拟现在)

If he should ask for me, tell him to phone me. 如果他来找我，叫他打电话给我。(从句用了表示将来的虚拟语气，而主句用了祈使句。)