I have been sitting in front of the monitor too long.

第一句话楼上回答正确,不累述了。至于第二句,包含主句和宾语从句。主句是：You said XXXXXX宾语从句是：You had seen her with him。对主句or从句提问要看表达的意思。如果表达“难道你没说过吗?”就对主句提问didn't you。表达“难道你没看到过吗”就对从句提问hadn't you。这里应该是对从句提问,从句主语是you,助动词是had,形式为肯定,所以反义疑问形式为hadn't you。这种“对从句进行反义疑问”的用法经常出现在以I开头表示个人看法意见的复杂句中,常见的主句形式有I think,I suppose,I believe,I guess,I reckon等。比如I don't think she's good at it,is she?但是从你的问题可以看出其他情况也是有此用法的。哥走了,给分。