it‘s at 6 o‘clock on ____evening该填什么

it's 6 o'clock 和at 6 o'clock有什么区别? it's at ten o'clock. let's make it at 3 o'clock on saturday afternoon ,为什么要用介词it? He is tired.He is on the s().It's seven o'clock.They are at --What's the time ---It's ____ eight o'clock .A.at B.on C.in L____ at the picture on the wall.It's very beautiful该填什么 By 8 o'clock ,at 8o'clock 和on 8o'clock什么区别 She gets up at seven o clock on _______(平日) 填什么英文 ( )is it now?It's nine o'clock.括号里填什么? It's twelve o'clock.Let's have____ ____上填什么 It's twelv o' clock.Let' s have [ ] 括号里应该填什么 It is o'clock on Monday m_____.中应该填什么