—I’m afraid you missed a fantastic lecture yesterday. How come you were absent from it?—If you _______ know, I asked for a day off and visited a relative of mine in hospital.

Passengers _____ fasten their seat belts immediately after taking their seats. The belts should remain buckled during the flight whether or not the “fasten seat belt” light is on.

—Look! The boy in the white shirt ___be Tom. --It ____be him. I saw him enter the library just now. 

--- ______ you give your seat to this old man? --- Of course. 

—Do you want to play basketball after school, Jack?—   . I have to practice my English.