you had better drop your parents a ________ in case (以防)they are worrying about you.
In a sport team each player has a clear role, and there are few occasions ______ members are confused or uncertain of their roles.
It is the test system, _____ the teachers, that is to blame for the heavy burden of middle school students nowadays.
With the help of his friends, he has _____a good business over the years.
Although it is ________ to watch programs on TV sometimes, I think people shouldn’t spend all the time watching it.
Modern teaching equipment as well as some computers _______ to the village school last week.