One of the most important questions they had to consider was _____ of public health. 
| A．what | B．this |
C．that | D．which |
--Can I help you with the heavy bag?
--______.
| A．Thank you. | B．It doesn't matter. |
| C．No, I am all right. | D．Really? |
That tree, _______ branches are almost bare, is very old.
| A．of which | B．on which |
| C．in that | D．whose |
As a rule, domestic servants doing odd jobs are paid_______.
| A．by hour | B．by an hour |
| C．by hours | D．by the hour |
Why don’t you bring ____ to his attention that you are too busy to do it?
| A．that | B．what | C．it | D．which |
He began to take political science ________ only when he left school.
| A．strictly | B．seriously | C．carefully | D．truly |