有人問了我這道有點難的語法題，大家可以先思考一下：

英語中有個虛擬語氣的句型“要不是...若不是...”——if it weren't for...

比如：If it weren't for you, I wouldn't be successful.（若不是你，我 不會成功。*事實上我成功了，而且歸功于你。）

另外，這個句型還可以用倒裝：Were it not for...，上述句子可以改成：

Were it not for you, I wouldn't be successful.

虛擬語氣的句型有個特點，時態(tài)要“退一格”，比如用過去時表跟現(xiàn)在情況相反，用過去完成時表跟過去情況相反。

所以 If it weren't for you 和 Were it not for you 都屬于跟現(xiàn)在情況相反，如果要表達跟過去相反的假設，要調(diào)整為 If it had not been for...或倒裝 Had it not been for...

但從句的形式要與主句的形式相匹配：

If it weren't for...的主干句應是 woud+do

If it had not been for...的主干句應是 would have done

來看圖中的句子（...）for your help, we'd never have been able to finish the project on time.（若不是你，我不可能按時完成這項任務。）

因為主干句用了“would have done“的形式，所以是一個跟過去相反的虛擬語氣，所以從句也要相應地用 If it had not been for 或者 Had it not been for。

對照一下選項，應該選 B。