She is so intelligent that she can________all the math problems.
--When _____ the abacus _____? -- In the sixth century by the Chinese people.
We have been friends for nearly twenty years. Nothing can break off our _______.
In our city, ________ college students want to work as a teacher in holidays.
I don’t like eating chocolate. The taste is too ________.
-- 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.