Gun control is a subject ____ Americans have argued for a long time.
| A．of which |
| B．with which |
| C．about which |
| D．into which |
Simon thought his computer was broken _______ his little brother pointed out that he had forgotten to turn it on.
| A．until | B．since |
| C．after | D．because |
Don’t be afraid of asking for help _______ it is needed.
| A．unless |
| B．since |
| C．although |
| D．when |
Food shortage will long be a worldwide problem _______ much has been done to supply enough for everyone.
| A．before | B．if |
| C．since | D．although |
I do every single bit of housework _______ my husband Bob just does the dishes now and then.
| A．since | B．while | C．when | D．as |
_______ the Atlantic Ocean crosses the equator, the trade winds cause a flow of water to the west.
| A．That | B．When |
| C．Where | D．Though |