5.In what
way do you think the sun cannot be harmful(有害的)？
A. The sun
can do harm to your eyes and skin.
B. It can
make rivers too dry.
C. Without
it there would be no life on Earth.
D. Hot sun
on dry land can cause fires.
Passage 12
Most animals
only have animals of a different kind for food. But sometimes two kinds of
animals come together in a partnership (伙伴关系) which is good for them. You may have noticed some birds on the backs of
sheep. This is not because they want a ride, but because they find easy food in
the parasites (寄生虫) on sheep. The sheep let the
birds do so because they can stop the parasites from troubling them. So though
they can do with it by themselves, they can do better together with each other.
Sometimes an
animal has a plant partner. The relationship develops until the two partners
cannot do without each other. This is so in corals of the sea. Inside their
bodies they have very small plants, which act as “cleaners”, taking the useless
things from the coral and giving oxygen in return. That is what the animal
needs to live. If the plants are killed, or are even kept from receiving light
so that they cannot live as usual, the corals will die.
