Lifeonlandprobablybeganabout430millionyearsago,thoughti...

来源：语文精选馆 2.01W

问题详情：

Life on land probably began about 430 million years ago, thought it had existed in the water for perhaps as long as 3,000 million years. When we think of the first life on land, we probably think of strange animals coming out of the oceans, but, in fact, no animals could have been living if plants had not been on land first. Plants had to be on land before animals arrived. They supplied the first land animals with food necessary to live, since they—the plants are the only form of life that is able to get and store energy.

The first plants to exist out of the water were probably certain kinds of algae（海藻）which were followed by other plants that grew close to the ground near water and needed water in which to reproduce. Once the move to land had been made, however, evolution（进化）took place quickly. By the end of 100 million years, plants had developed their roots, and some developed tall tree-like forms, since height was very important in competition for sunlight. About 300 million years ago, much of the world was covered with forests of huge trees.

In most ways they were like modern trees. They had roots, leaves, wood, but mostly they had not developed seeds.

29. The main idea of the first paragraph is .

A. life on land probably began about 4,300 years ago

B. the first animal on land came from oceans

C. there wouldn't be animals without plants

D. plants are the only form of life that is able to get and store energy

30. Which of the following is TRUE?

A. Algae have existed for more than 430 million years

B. It is impossible that algae might be the earliest plant on land

C. Plants get food from animals in the oceans

D. Evolution began after animals appeared on land

31. Plants with roots appeared about _______ million years ago.