单选

Passage2
Questions 6 to 10 are based on the following passage.
It is difficult to form a correct idea of a desert without having seen one. It is a vast plain of stands and stones, with mountains here and there of various sizes and heights, without roads or shelters. They sometimes have springs of water. The most remarkable of deserts is the Sahara. This is a vast plain, but title elevated above the level of the ocean, and covered with sand and gavel (砂砾）, with a mixture of sea shells.

Amid the desert, there are springs of water, which burst forth and create verdant (翠绿的) spots, called oases. There are thirty- two of these which contain fountains, and date and palm trees, twenty of them are inhabited. They serve as stopping places for t
In 1805, a caravan consisting of 2,000 persons and 1,800 camels, not finding water at the usual resting place, died of thirst, both men and animals. Storms of wind are more terrible in this desert than on the ocean. Vast surges and clouds of red sand are
If, unfortunately, any one falls sick on the road, he or she must either endure the fatigue of traveling on a camel, which is trouble some even to healthy people, or he or she must be left behind on the sand, without any assistance, and remain so until a
A.there is nothing green in a desert
B.the Sahara is high above sea level
C.a real desert can hardly be imagined
D.a mixture of sea shells is part of a desert

参考答案