24. The Niagara Waterfalls, ______ is shaped like a semicircle, are 670meters wide, and fall 56 meters in an awesome white sheet of water.
| A．what | B．where | C．the largest of which | D．in which |
_______ he said was to the point..
| A．That | B．What | C．Which | D．As |
The boy ______ is talking to our foreign teacher is our monitor.
| A．which | B．whose | C．who | D．whom |
Drivers usually have _____ good sense of direction.
| A．a | B．an | C．the | D．/ |
Make sure that your computer room is 100%________of insects because they can really cause trouble to your machine.
| A．absent | B．rare | C．free | D．short |
Things lost sometimes just turn up________you never expect to find them.
| A．unless | B．where | C．after | D．as if |