Sharks may be able to smell blood from miles away, but they probably don’t know how red it is. It is likely that they only see the world     in black and     white     according to     a study that is the first to investigate sharks’ visual system.

A team at the University of Western Australia studied the visual systems of many different species of sharks and what they have found is diversity in eye design that mirrors the ecological and behavioral diversity of the shark species. The team looked at the retinal cells of 17 species of sharks caught off Queensland and Western Australia and found out that the cells are responsible for sharks’ color blindness.

According to the study, these animals are color-blind due to the light receptors they have got in their eyes. There are two main types of light-sensitive cells to allow animals to see: rod cells help measure brightness because they are highly sensitive to light and allow night vision but cannot tell colors apart, while various types of cone cells help distinguish colors. They peeked at the structure of sharks’ rod and cone cells in the retina. Human eyes come with red, green and blue cone variations, while sharks appear to have just one kind of cone cells.

The study suggests that contrast against the background, rather than color itself, might be more important for object detection by sharks. Costumes that camouflage swimmers’ bodies in sea water are less likely to draw a shark’s attention than ones with bright, solid colors that emphasize their outline. “It’s the high contrast against the water rather than the color itself which is probably attractive to sharks,” said Professor Nathan Hart who led the study.

【小题1】What is paragraph 2 mainly about?

A．The importance of the research.

B．The features of sharks’ retinal cells.

C．The process and the result of the study.

D．The functions of sharks’ visual systems.

【小题2】What causes sharks’ blindness to color according to the study?

A．Their fragile rod cells.	B．Their lack of various cone cells.
C．Their dark living environment.	D．Their weak sensitivity to light.

【小题3】What does the underlined word “camouflage” in the last paragraph probably mean?

A．hide

B．fit

C．beautify

D．protect

【小题4】What is the main purpose of the passage?

A．To clear up a wrong belief.	B．To raise funds for a program.
C．To show a unique phenomenon.	D．To present a scientific discovery.