6. You might not go there yesterday. 7. You should go there: they are waiting for you. 8. You had to go there yesterday. 9. You didn't have to go there yesterday. 10. We may come to you tomorrow. 11. Where are they living now? They may be living abroad now, but I am not sure. 12. You should listen to him and try not to worry about it.
16) A
17) C
18) B
19) C
20) A
21) A
1)There is,it is
2)There are,they are
3)There are,they are
4)There is,it is
I see Sam
I lake caks
He has got a red pen