About ten men in every hundred suffer from color blindness in some way. Women are l________. Only about one in two hundred is affected by this matter. Some people say it is s________ to be driven by woman.

There are different f________ of color blindness. In some cases a man may not be able to see deep red. He may think that red, orange and yellow are all shades（色调）of green. Sometimes a person cannot tell the difference between blue and green. An unlucky man may s________ see everything in shades of green-a strange world indeed.

Color blindness in humans is a strange thing to e________. In our eyes there are millions of very small things called "cones". These help us to see in a bright light and to tell the differences between colors. There are also millions of "rods", but these are used for seeing when it is nearly dark. They show us shapes but no color.

Some insects have favorite c________. Mosquitoes (蚊子) like blue but do not like yellow. A red light will not attract insects, but a blue lamp will. In a s________ way human beings also have favorite colors. Yet we are lucky. With the help of the cones in our eyes we can see many beautiful colors by day, and with the help of the rods we can see shapes at night. One day we may even learn more about the invisible (看不见的) colors around us.