—Is there any vaccine(疫苗) against H1N1 flu that can be used on humans?
—No, but scientists are working to develop ________ .
| A．that | B．it | C．one | D．so |
If you ____________ Mary, ask her to come and see me.
| A．lose sight of | B．catch sight of |
| C．are in the sight of | D．are at the sight of |
It was in the university ten years ago, _________ they met in September for the first time, _________ they fell in love with each other.
| A．that; when | B．when; that | C．that; where | D．where; that |
Professor Smith, along with his assistant, ________on the project day and night to meet the deadline.
| A．work | B．working | C．is working | D．are working |
Some researchers believe that there is no doubt ______a cure for AIDS will be found.
| A．which | B．that | C．what | D．whether |
If you go by _________train, you can have quite a comfortable journey, but make sure that you get＿fast one.
| A．the; the | B．/; a | C．the; a | D．/; / |