He says he will be back —— 10 o'clock.为什么 用 at 而不用in?

He says he will be back —— 10 o'clock.为什么 用 at 而不用in? It's eleven o 'clock .He will be back at twelve .= he asked you to call him back at 10 o'clock,back at 10 o'clo he will be away for two months中为什么用for而不用in —____ will he be back?—In ten days. we will be back/ in / six o'clock.可是答案是at He says he will be back two days but he comes back a week. He will come back after ten o'clock同义句 He will come back ( )eight o'clock( )the morning. he's always back home at five o'clock,____he? It`s 10 o`clock now.He __be back at any time.为什么填空是should而不是 He will be back———— two weeks‘ time.A.at B.in C.after D.for