_______ there are many different types of food, some animals spend their lives eating only one type.
___ you know the rules of swimming, you will be able to swim well.
Being League members, ___ we ought to work hard at our lessons;___ we ought to take an active part in social activities.
___ the clock structk twelve. I got home with my brother.
____ for a bus, I was reading a magazine.
Knowing how long the test would last, the students who finished ____ back and waited until the end of the exam.