When Marx was in London, he  __   read at the library for hours.

 –Look! The boy is running fast! –He might ______ to catch a bus.

Susan’s parents bought a large house with a swimming pool. It ______be very expensive.

---I think Helen is at home.---No, she    be at home, for she phoned me from the airport just five minutes ago.

—Must I go there right now?—No，you ________.You ________ go there before supper.