_____all the representatives still not there ，the meeting was postponed for several hours.
A、BecauseB
with加名词短语，表示原因，本句意思为：“因为所有的代表还没有到场，会议被推迟了好几个小时”。而because(因为)引导的是原因状语从句，其后必须是个从句。by为“到⋯⋯为止”。
Yourbikeneeds_____.You‘dbetterdoirightnow.
_____youunderstandthisrule，you‘llhavenodifficultyindealingwithsuchproblems.
My wallet is nowhere to be found.I_____it when I was on the bus.
I ‘ve been telling you_____not to do that ，but you neve listened to me.That ’s why you gotinto trouble.
He‘s working hard_____.
