Edison never stopped ___ new and better ways to do things.
| A．to search for | B．searching for | C．to search | D．searching |
---I haven’t got the reference book yet, but I’ll have a test on the subject next month.
---Don’t worry. You______ have it by Friday.
| A．could | B．shall | C． must |
D．may |
I sincerely request the honor of your _______ at my son’s birthday party to be held next Sunday.
| A．admission | B．entrance | C．permission | D．presence |
The roof fell ______ the PLA men had time to rescue the child trapped in the house.
| A．until | B．unless | C．before | D．because |
When he ______ the front door, he found his keys were nowhere.
| A．would open | B．opened | C．had opened | D．was to open |
The university with two____ campuses has a student population of 50,000 in total．
| A．unique | B．separate | C．single | D．alternative |