i am not sure where i should have left it这句话是什么从句?为什么sure后面可以直接跟一个句子

I am not sure是什么意思 Er...i am not sure. Where is Lucy I am not sure.she( ) in the classroom.Amaybe Bmay be Cprobably Dmight i am not sure.where did he go?合为一句 i am not sure—— —— —— I'm sure I am not wrong i am not sure反义疑问句 I am not sure what your talking 翻译成中文：I am not sure i am not sure 什么意思 I am not sure同义句 maybe.but I am not sure. Sure.I am not a bad I AM NOT SURE YET?什么意思? I am not sure.that I am gay I am not sure what else to I am not sure what else to say. I am not sure yet同义句I am not sure yet=? may be,I am not sure还是maybe,I am not sure? i am not sure where i should have left it这句话是什么从句?为什么sure后面可以直接跟一个句子