at...o'clock 和 by...o'clock 辨析.

at...o'clock 和 by...o'clock 辨析. By 8 o'clock ,at 8o'clock 和on 8o'clock什么区别 英语：by around eight o'clock是否等于at about eight o'clock?英语：by around eight o'clock是否等于at about eight o'clock? They must _____(be)at school by eight o'clock by ten o'clock 12o'clock at he is always home by eleven o'clock.be home怎么是回家的意思 和is at home样么 They should be at school by eight o'clock.句中为什么用by? I'm supposed to be at home by ten o'clock at night. I'm supposed him to be at home by ten o'clock at night.什么意思? marry has to stay at home by ten o'clock at night改为一般疑问句 They should__school by eight o'clock.A are B be at C are at D be it's 6 o'clock 和at 6 o'clock有什么区别? School at nine o’clock Lucy .at eight o’clock. at _____ twelve o’clock at 7o'clock是什么意思? I have to be in bed by ten o'clock.这句中 by ten o'clock是什么意思,为什么不是at,have to be in bed 是什么句型.