Passage 4 It had been getting colder all day, and the wind had risen at nightfall and was blowing like fury, which I have never before experienced in a tent. The thin canvas flapped and cracked wildly . The gusts of wind grew stronger, each one worse than the last. It was only three yards away to the edge of Everest ’ s northeast precipice and the wind was blowing straight over it. Suddenly one tent-rope tore loose. We realized we ought to have fixed them more firmly. One side of the tent billowed in. We tried to straighten the canvas but it was impossible to do so. If another rope went we might be blown,the tent and all,over the precipice. Somehow I managed to get out of my sleeping-bag, dragged on my wind-proof trousers and jacket. The tapes closing the tent-flaps had become stiff with ice ; it was impossible to unlace them in gloves so I had to take them off ; and by the time I had done so in bare hands,my fingers became frozen. I crawled out of the tent. It was still snowing hard, but it was not completely dark, and I could just see the loose tent-rope. It had pulled away from two large stones to which we had fixed it ; the wind had been so strong that these stones, which must have weighed a hundredweight, had been pulled right over. It was not easy to refix the rope, but I managed it. Then I had to crawl round on hands and knees —it was not safe to stand in the wind—in order to find more stones to hold the rope firmly. At last I struggled hard back into the tent and flopped down exhausted on my sleeping-bag. After an hour or so I managed to get the blood moving in my frozen fingers but my feet stayed like pieces of cold stone all night. It was partly for this reason and partly because of the storm that I did not sleep at all. 21.The word “wind-proof” means __________ . A. against wind B. strengthening wind C. producing wind D. for wind