中断是CPU与外部设备数据交换的重要方式。CPU响应中断时必须具备3个条件，分别为外部提出中断请求，本中断未屏蔽， (4) 。CPU响应中断后，必须由 (5) 提供地址信息，引导程序进入中断服务子程序；中断服务程序的入口地址存放在 (6) 中。

A．中断源

B．中断响应

C．允许中断

D．中断向量表

In June 1985, two British mountaineers Joe Simpson and Simon Yates made the first-ever climb of the 21,000-foot snow-covered Siula Grande mountain in Peru. It was an exceptionally (26) job, but nothing compared to what was to (27) . Early in the process, Simpson (28) and broke his right knee. Yates could have (29) him but managed to find a way of (30) him down the mountains on a rope in a series of difficult drops. Then Simpson fell into a crevasse and Yates eventually had no (31) but to cut the (32) , completely convinced that his friend was now (33)

In his book on the (34) , Joe Simpson wrote:

(35) I looked at the distant moraines, I know that I must at least try I would probably (36) there among those rocks. If I died, well, that wasn’t so (37) , but I wouldn’t have (38) waited for it to happen. The (39) of dying no longer affected me as it had in the crevasse at first. I now had a chance to (40) it and struggle against it.

The survival of Yates himself was (41) . That Simpson somehow found a way of (42) out of the crevasse after 12 hours and then crawled and (43) himself six miles back to camp, (44) three days and might without food or drink, would be considered as a heroic fiction. But in fact it was so (45) .

28().

A. bent

B. fell

C. raised

D. survived