b1
2:A
6:b
7:b
8:b
b2
1.tuan has already done his homework
2.to get/asking
3.was raining
4.went
5.were watching
b3
1.was invented....by..
2are produced....by..
3his sister like to cooking
4if halongbay in the northen.vietnam
5difficult for me to understand
6very simple to use a computer