Geography is the study of the countries of the world and of such things ______ the land, seas, climate, towns, and population.
Nobody can explain the mystery ____ he suddenly disappeared.
It suddenly___ to me that we could use the computer to do the job.
Though she _______for a moment, she finally went in and asked to see a dress that was in the window.
The survey shows that a large number of teenagers are ________ cigarettes nowadays.
Rita _________two hours every Sunday afternoon to spend with her son.