You never imagine what trouble I have had ______ your house．It took me nearly 2 hours．

A．to find

B．finding

C．found

D．for finding

从煤岩显微组分看，对同一种煤而言，最难氧化的是（）。

A、镜质组

B、丝质组

C、稳定组

D、半镜质组

E、矿物质组