exercise 1 : Chia dạng đúng của động từ trong ngoặc 
1 put on a raincoat . It ............(rain). It ................(rain) a lot in summer
2 where are children ? They ....................(read) books in the library 
3 I ..............(have) four exams so far this month
4 Mr Tan ............(teach ) in this school for over ten years 
5 you..........(not stop) talking since you got here !
6 scientists .............. ( find ) more than 30 unknown insects
7 yesterday , my mother ........( give ) many books for me 
8sim............... ( agree ) to lend me his calculator last lesson 
9 my old teacher ........... ( teach ) Maths yesterday 
10 We ............ ( not decide ) what to get Mark for his birthday yet 
11 I ........... (already/finish) my homework . It was easy ! 
12 jorge ............ ( not play ) tennis since his injury
13 my parents ......... ( be ) to Australia three times