no modern telecommunications, we would have to wait for weeks to get news from around the world.
| A．Were there | B．Had there been | C．If there are | D．If there have been |
21._____by a desire to learn, he was not interested in children’s play and adventure when he was young.
| A．Driven | B．Driving | C．To drive | D．To be drive |
20. The flu is believed________by viruses.
| A．causing | B．being caused | C．to be caused | D．to cause |
19. They________a lot of suggestions for improving the workers’ living conditions.
| A．put out | B．put forward | C．put on | D．put in |
18. After having gone____-far, I didn’t want to turn back.
| A．enough | B．thus | C．that | D．Much |
17. One of the mottos for the park makes_____clear that science and business can and must work together to build the future.
| A．them | B．it | C．us | D．This |