Can you explain ____ most deserts are located near the west coast of the continents?
| A．why is it that | B．why it is that |
| C．how it is that | D．how is it that |
It is so cold that you can’t go outside _____ fully covered in thick clothes.
| A．if | B．unless |
| C．once | D．when |
As you go through this book, you ________ that each of the millions of people who lived through World War II had a different experience.
| A．will find | B．found |
| C．had found | D．have found |
It was when we were returning home ________ I realized what a good feeling it was to have helped someone in trouble.
| A．which | B．that |
| C．where | D．how |
______ scientists have learned a lot about the universe, there is much we still don't know.
| A．Once | B．Since | C．Though | D．Unless |
If you come to visit China, you will ______ a culture of amazing depth and variety.
| A．develop | B．create |
| C．substitute | D．experience |