有人问了我这道有点难的语法题，大家可以先思考一下：

英语中有个虚拟语气的句型“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 不会成功。*事实上我成功了，而且归功于你。）

另外，这个句型还可以用倒装：Were it not for...，上述句子可以改成：

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

虚拟语气的句型有个特点，时态要“退一格”，比如用过去时表跟现在情况相反，用过去完成时表跟过去情况相反。

所以 If it weren't for you 和 Were it not for you 都属于跟现在情况相反，如果要表达跟过去相反的假设，要调整为 If it had not been for...或倒装 Had it not been for...

但从句的形式要与主句的形式相匹配：

If it weren't for...的主干句应是 woud+do

If it had not been for...的主干句应是 would have done

来看图中的句子（...）for your help, we'd never have been able to finish the project on time.（若不是你，我不可能按时完成这项任务。）

因为主干句用了“would have done“的形式，所以是一个跟过去相反的虚拟语气，所以从句也要相应地用 If it had not been for 或者 Had it not been for。

对照一下选项，应该选 B。