There is a system ________the waste is disposed of using the principles of ecology.
| A．which | B．where | C．that | D．at which |
Life is filled with things we have no control over, ________ ourselves, we can control.
| A．for | B．and | C．so | D．but |
I'll make some sandwiches, just ________ we get hungry later.
| A．even if | B．as though |
| C．if only | D．in case |
You know that some people say more but do less ________ others do the opposite.
| A．once | B．while | C．when | D．as |
The professor told me to start the research right now, ________ I was sure to fall behind.
| A．or | B．so | C．but | D．and |
________ a man's age, he can reduce it several years by wearing a confident smile.
| A．Whichever | B．Whatever |
| C．Whenever | D．However |