1.He is not in school today ,maybe he is sick.
2.You didn't complete your homework,you must be watching TV yesturday.
3.Be quik,you mum is waiting for you at home.
4.I might go to Beijing next week.
5.Mr Lee can't be in Beijing,because i just saw him at the mall few minutes ago .
6.It's impostable that it had rained yesturday.
7.They just bought a new car,they must be very rich.
8,.She can't be Mary,Mary is sick
9.Perhaps he is doing his homework.
10.Maybe he has already known this news from newspaper.