Exactly______ the potato was introduced into Europe is uncertain, but it was probably around 1565.
| A．whether | B．why | C．when | D．how |
—Shall I open the window to let in some fresh air?
—______ It’s really hot in here.
| A．What a pity. | B．Sure, go ahead. |
| C．Why not? | D．It’s up to you. |
Though he didn’t perform well in the French Open, he is still ______ the top ten in the world.
| A．among | B．of | C．in | D．above |
—Where’s my driving license? Maybe I left it at home.
—My Goodness! I ______ you would always take it along.
| A．was to think | B．thought |
| C．have thought | D．have been thinking |
Though the training cost a lot of time and effort, I do think it ______.
| A．valuable | B．significant | C．worthwhile | D．vital |
After careful consideration, he decided to take the position, ______ he knew it would be difficult for him.
| A．even though | B．now that | C．as if | D．so that |