(2013·天津，9)No one________ be more generous；he has a heart of gold.

—Where did you get this book?—I picked it up from a second-hand bookshop if you ______ know.

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

The boy        be very naughty, but he is very lovely.

When we were young, every evening my brother and I ______ stay at home waiting for our mother.