Directions (1-4) : Read the following passage carefully and answer each of the questions given below it in the context of the passage.

We started pitching the highest camp that has ever been made. Everything took five times as long as it would have taken in a place where there was enough air to breathe, but at last got the tent up and when we crawled in, it was not too bad. There was only a light wind and inside it was not too cold for us to take off our gloves. At night most climbers take off their boots, but I preferred to keep them on. Hillary on the other hand, took his off and led them next to his sleeping bag.

Question-4 : They crawled into the tent because-