I like do the things that the things are difficult.我喜欢做那些难的事情.
I don't think that you can do this thing.我不认为你能够做那件事.
I like the pencil which in your pencil case.我喜欢你铅笔袋里的那支铅笔.
I need to use the pen which on the desk.我需要书桌上的那只钢笔.