Why not ______ an English-English dictionary for yourself?—I have already had ________.

Which subject do you like better, Chinese or Maths?— . I prefer English.

Look at the boy running on the playground. Is it David? —- It ______ be him. I saw him go to the teachers’ office just now.

Generally speaking, a computer works _______________ a human brain.

He is very clever. At age 6, she _____to play the piano.