The natural world is colorful with humans，plants and animals showing different colors.

    Human skin can be many different colors and it changes.with the sun，our feelings or our health for example.This is because of pigments（色素），which reflect light and make what the eye sees as colors.So，when we feel excited or angry，our heart can send more blood to the face and the pigments in the skin become red.This is why we have the expression that someone. "sees red"when they are angry.

    Plants also have pigments.Color is important for them to live on.The bright colors of flowers catch the attention of insects（昆虫），which then carry their pollen（花粉）from one flower to another.Bees can see colors we cannot，and they follow these to the inside of the flower.Without bees visiting flowers in this way，many plants would die out.

    Animals also use color for their own need.They protect themselves with different colors so as not to be seen by predators.The snowshoe hare for example，a type of wild rabbit，changes color with seasons for this reason.During summer it is a brown color，and in winter it is white so that it can hide in the snow.However，some animals use color as a warning to make predators stay away.Bright colors such as yellow and red are often used in this way.Nature，however，is very clever，and predators also use colors to attract（吸引）the animals they feed on..

    So，we can see that there may be many different reasons and uses for colors in the natural world.Some uses of color in nature remain unknown；but one thing is for sure，color not only makes our planet beautiful but it is also necessary for our planet to live on.

（1）Paragraph 2 mainly tells us that 　 　 is/are the cause that makes human skin change color.

A.feelings

B.pigments

C.Blood

D.sunshine

（2）According to Paragraph 3，plants can use 　 　 to attract insects.

A.leaves

B.fruits

C.pollen

D.color

（3）The underlined word"predators""in Paragraph 4 refers to animals which 　 　.

A.hide in secret places

B.kill other animals for food

C.change color with the sun

D.protect themselves from danger

（4）What is the main purpose of the passage？ 　 　

A.To describe animals' ways of life.

B.To encourage us to study color in nature.

C.To introduce the uses of colors for life on earth.

D.To explain the importance of protecting our planet.