题目内容：

People living more than three thousand meters above sea level find it difficult to raise vegetables all year long. People living in the highlands of Peru and Bolivia, for example, cannot grow vegetables outdoors during the months of May through September. It is very cold in the highlands at that time of year. If traditional farming methods are used, vegetables will not survive.

However, there is another way to grow vegetables throughout the year in cold areas. It is a method of gardening developed by a private agency called World Neighbors. The method uses “hot houses” built below ground. A hot house is a building covered with plastic or glass in which vegetables or flowers are grown. The traditional hot house is built above ground.

The air temperature is cold in the highlands of Peru and Bolivia during the winter. But, the winter sun is hot. So, World Neighbors advises farmers there to build hot houses below ground. The design is simple. The material does not cost much. Here is how World Neighbors says to build it: Dig a hole two and one-half meters wide and six meters long. Make it about two meters deep. Build wall with a door in one end of the hole. Dig steps from the ground down to the door.

Now, build a wall along the top edge of the hole. Make it about one-half meters tall. Earth bricks work fine. Build two shorter walls on the ends. These will be uneven; one side will be as high as the existing wall. The other side will be at ground level. Leave a small opening in each of these sloping walls. This prevents the hot house from becoming too hot. Now, make the roof. Build a wood frame. Cover it with clear plastic. Connect it to the brick walls.

The underground hot house we have described is large enough for two raised vegetable beds. Each is one meter wide and six meters long. Each is seeded and watered just as if it were in a garden above ground.

The dirt walls protect the growing plants from the cold. The clear plastic roof permits the sun’s heat to enter. At night, the roof should be covered with straw. This helps prevent cold air from entering. An under ground hot house this size will provide enough vegetables for one family. Groups needing more vegetables can make it bigger.

66. If you lived in Peru, you _______.

A. should raise the special kinds of vegetables that can endure cold

B. could not plant at all

C. had to work out some new unusual plans

D. would not have many vegetables to eat

67. To our surprise, the “hot houses” invented by World Neighbors are _______.

A. covered with a transparent plastic ceiling

B. built under ground

C. quite small

D. hotter than traditional ones

68. The hot house can be kept warm by using _______.

A. a big oven  B. an electricity heater

C. the heat of the earth’s interior   D. the sun shine

69. The measure to prevent the hot house from becoming too hot is to _______.

A. make the roof sloped B. dig holes on the walls

C. make the wall not vertical D. make the walls shorter than the ground level

70. According to the passage, the method suggested by World Neighbors is _______.

A. new and difficult      B. uneasy to explain

C. at trial step D. simple and practical