几道英语单选 1.He stood there ____,not knowing what to do .A helpl

几道英语单选
1.He stood there ____,not knowing what to do .
A helplessly B helpless
为什么选B 不选A
2.I did very ____the first time I took my entrance examination .
A .poorly B .poor
为什么
3.The staff in office do not consider their boss ____any more after they have known that he forges his certificate .
A .respective B .respecting C .respectable D .respectful
为什么