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Trees are our best friends. They give us clean air. They also give us places to stay out of sun, fruits, vegetables, flowers, medicine, wood etc. Trees help our environment in many ways. They don’t let soil wash away because of the heavy rain. They keep water, so the land will not become dry. If there are no trees, our country will turn into desert. Animals will leave or die. People will get sick from air pollution. However, there are not enough forest lands in our country. So, people should know the importance of planting more trees. The mass media like TV and radio can help a lot. To live a healthy life, we have to plant more trees.
1．Trees are our best friends because they give us a lot.2．Trees can keep soil and water.
3．Animals will die and people will be sick without trees.
4．Our country has enough forest lands.
5．The mass media can help people know the importance of planting trees.
同类型试题
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
y = sin x， x∈R， y∈[–1，1]，周期为2π，函数图像以 x = (π/2) + kπ 为对称轴
y = arcsin x， x∈[–1，1]， y∈[–π/2，π/2]
sin x = 0 ←→ arcsin x = 0
sin x = 1/2 ←→ arcsin x = π/6
sin x = √2/2 ←→ arcsin x = π/4
sin x = 1 ←→ arcsin x = π/2
