虚拟语气 请大家看看这两个句子 我总觉得答案不对

虚拟语气 请大家看看这两个句子 我总觉得答案不对
1.Were it for their help,we (not overcome)______the difficulties.
答案是would not have overcome
我觉得这个句子不对 应该是Had it not been for their help,we would not have overcome the difficulties.如果是Were it for their help,的话 那就是时态不对了 were是表示的与现在事实相反 而had才是与过去相反的 这个句子从意思上看应该是已经发生过的 应该用过去时吧
我的这个理解对吗?
2.---Did you visit Los Angeles on your vacation?
---If I would have a week off.
这个题是个改错题 答案是把would have改为had
我觉得应该是改为had had 应为问句是did you 那就是发生过了 回答人从句中应该说If I had had a week off,I would have visit Los Angeles on my vacation