详细分析! English help!

详细分析! English help!
1.He showed me into the room,where many books were left ____here and there .
A lay B lying C laid D to lie
为什么是B?
2.Although he realized the man had been lying(为什么是lying,两题不是不一样吗?）.he knew he must not accuse him directly .
A.lay为什么不可以?况且摆放的分词应该是laying .为什么不是laying
两个意思和用法有什么不一样?
第二题的lying 是撒谎的意思,两个应该不一样啊!我搞不明白这个问题.请帮忙详细分析