1.Life on land probably began about 430million years ago,thought it had existed in the water for perhaps as long as 3,000million 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(進(jìn)化)took place quickly.By the end of 100million years,plants had developed their roots,and some developed tall tree-like forms,since height was very important in competition for sunlight.About 300million 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.
28The main idea of the first paragraph isC.
A Life on land probably began about 4,300years 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
29Plants with roots appeared aboutC million years ago.
A.430
B.330
C.300
D.100
30 The first trees were like modern trees in most ways except thatC.
A They do not have branches
B.They do not have flowers
C.They do not have seeds
D.They do not need sunlight.