You see the lightning _____ it happens, but you hear the thunder later.
| A．the instant | B．for an instant | C．on the instant | D．in an instant |
— Mrs.Smith,please teach me how to draw on the computer today.
—Oh,no. ____.You have to get familiar with the keyboard first.
| A．It is never too old to learn |
| B．Think twice before you do |
| C．Learn to walk before you run |
| D．One today is worth two tomorrows |
Overpopulation is a terrible threat to the human race.Yet it is probably ____ a threat to the human race than environmental destruction.
| A．no more | B．not more | C．even more | D．little more |
Ladies and gentlemen,welcome to my program.____ me this evening is Dr.Gray.
| A．To join | B．Join | C．Joined | D．Joining |
While income worry is ____ rather common problem of the aged,loneliness is another problem that ____aged parents may face.
| A．a;/ | B．the;/ | C．a;the | D．the;the |
Many people can not learn any lessons from the mistakes____they get hurt somehow.
| A．whether | B．unless | C．if | D．when |