I __ very carefully,but I can ____ nothing.

I __ very carefully,but I can ____ nothing. 改错I listened carefully,but nothing heard. I can do nothing but 选 择 ------ her carefully ,but I --- --nothing .见下面补充 英语：I ___ around but ____ nothing. I am very tired but I can't____ ____ ____(休息) Nothing but tears.I can do anyting! but I n____ to listen very carefully to understand it 1.Jack ____ carefully but he can ___ nothing in the room. Nothing i can change,but i can wait、什么意思? I____my teacher carefully,but I can't _____her. I listened carefully but I heard nothing各个单词在句中起什么成份?