---We will have a picnic next month. ---Really? __________great fun!
You _______ wash your hands before meals. It is good for your health.
You _______ walk across the road. It’s dangerous.
You’d better _______ too much meat. You are much too fat.
You should _______ the doctor’s advice and _______ the medicine on time.
_______ necessary for us _______ our environment clean and tidy.