What happened to Mike? —He had a stomachache. He began to work _______ having breakfast this morning.[ ]

Which module is the most difficult in this book?— I think _____ module.

The meat is ___ expensive and eating ___ meat is bad for your health.

I bought a new sweater last weekend. It________me 120 yuan.

My parents will buy a piano for me if I _____ good grades in the tests.