DNA is very useful for us, it many years ago.
A. discovers
B. discovered
C. is discovered
D. was discovered
If we have a ten-day holiday, we London with my parents.
A. visit B. were visiting C. will visit D. visited
I my friend Tim for 5 years.
A. know B. have known
C. knew D. will know
— Peter, where is your brother?
— He his English homework.
A. is doing B. does C. will do D. did
— Jack, you swim?
— Yes, I can.
A. can B. may C. need D. must
The elephant’s legs are than the dog’s.
A. strong
B. stronger
C. strongest
D. the strongest
