--When _____ the abacus _____? -- In the sixth century by the Chinese people.
A. is, invented B. did, invent
C. was, invented D. does, invent
We have been friends for nearly twenty years. Nothing can break off our _______.
A. friendship B. pleasure
C. decision D. experience
In our city, ________ college students want to work as a teacher in holidays.
A. thousand
B. thousands of
C. thousand of
D. two thousand of
I don’t like eating chocolate. The taste is too ________.
A. crispy B. delicious
C. salty D. sweet
-- Look at the boy running on the ground. Is it David?
-- It _______ be him. I saw him go to the teacher’s office just now.
A. might B. could
C. can’t D. mustn’t
They’ve got two machines, but ________ works well.
A. neither B. either
C. all D. both
