First to colonize the barren land are the lowly lichens, surviving on bare rock.

　　Slowly, the acids produced by these organisms crack the rock surface, plant debris accumulates, and mosses establish a shallow roothold. Ferns may follow and, with short grasses and shrubs, gradually form a covering of plant life. Roots probe even deeper into the developing soil and eventually large shrubs give way to the first trees. These grow rapidly, cutting off sunlight from the smaller plants, and soon establish complete domination—closing their ranks and forming a climax community which may endure for thousands of years.

　　Yet even this community is not everlasting. Fire may destroy it outright and settlers may cut it down to gain land for pasture or cultivation. If the land is then abandoned, a secondary succession will take over, developing much faster on the more hospitable soil. Shrubs and trees are among the early invaders, their seeds carried by the wind, by birds and lodged in the coats of mammals.For as long as it stands and thrives, the forest is a vast machine, storing energy and many elements essential for life.

　　26.What does the forest strike mankind as permanent?

　　A) The trees are in community.

　　B) The forest is renewed each season.

　　C) Man's life is short in comparison.

　　D) It is an essential part our lives.

　　27.What has sometimes caused plants to die out of the past?

　　A) Interference from foresters.

　　B) Variations in climate.

　　C) The absence of wooded land.

　　D) The introduction of new type of plants.

　　28.In a “primary succession', what makes it possible for mosses to take root?

　　A) The type of rock.

　　B) The amount of sunlight.

　　C) The amount of moisture.

　　D) The effect of lichens.

　　29.What conditions are needed for shrubs to become established?

　　A) Ferns must take root.

　　B) The ground must be covered with grass.

　　C) More soil must accumulate.

　　D) Smaller plants must die out.

　　30.Why is a “secondary succession” quicker?

　　A) The ground is more suitable.

　　B) There is more space for new plants.

　　B) Birds and animals bring new seeds.

　　D) It is supported by the forest.

　　Questions 31 to 35 are based on the following passage:

　　Grandma Moses is among the most celebrated twentieth century painters of the United States, yet she had barely started painting before she was in her late seventies. As she once said of herself: “I would never sit back in a rocking chair, waiting for someone to help me.” No one could have had a more productive age.

　　She was born Anna Mary Robertson on a farm in New York State, one of five boys and five girls.(“We came in bunches, like radishes.”) At twelve she left home and was in domestic service until, at twenty seven, she married Thomas Moses, the hired hand of one of her employers. They farmed most of their lives, first in Virginia and then in New York State, at Eagle Bridge. She had ten children, of whom five survived; her husband died in 1927. Grandma Moses painted a little as a child and made embroidery pictures as a hobby, but only switched to oils in old age because her hands had become too stiff to sew and she wanted to keep busy and pass the time. Her pictures were first sold at the local drugstore and at a fair, and were soon spotted by a dealer who bought everything she painted. Three of the pictures were exhibited in the Museum of Modern Art, and in 1940 she had her first exhibition in New York. Between the 1930's and her death she produced some 2,000 pictures: detailed and lively portrayals of the rural life she had known for so long, with a marvelous sense of color and form. “I think really hard till I think of something really pretty, and then I paint it.”she said.