Teachers have to constantly update their knowledge in order to maintain their professional ___.
Eating too much fat can ________ heart disease and cause high blood pressure.
Mr. Lee, may I ask you a question? —______.
—Excuse me! Sir, is the swimming pool open all day? —.Only from 6:00 p.m. to 10:00 p.m.
We’d better discuss everything _______ before we work out the plan.
The next thing he saw was smokefrom behind the house.