The Bunsen Burner is so named because it is thought ___________ by Robert Bunsen.
| A．to be invented | B．having been invented |
| C．invented | D．to have been invented |
. ______ the ancient Egyptians built the pyramids puzzled people for centuries.
| A．Whether | B．What | C．How | D．Where |
No one but the experts in this field can _____ the difference between them.
| A．recognize | B．speak | C．spot | D．predict |
—Who______ it be that is knocking at the door?
—It ______ be Father, but I’m not sure.
| A．can; must | B．can; may | C．must; can | D．may; must |
The meeting we had ________ to _______ us finally.
| A．looked forward; disappointing | B．been looked forward; disappointed |
| C．looked forward; disappointed | D．been looked forward; disappointing |
The great _____ of this computer is that it’s so cheap compared to the others.
| A．power | B．strength | C．energy | D．force |