Scientists (科学家) think that many animals cannot see colours. The world is black and white to them. Scientists want to find out if (是否) dogs can see colours. When the scientists give the dogs food, they show them a certain( 一定的 ) colour every time. The dogs get ready to eat when they see this colour. The scientists then show the dogs another colour. Again the dogs get ready to eat. The colours are all the same to them. Colours are not all the same to monkeys. For example, if we put food in a red box, and do this every day, a monkey will always go to the red box to get food. If we put food in a blue box, the monkey won’t go to it.

（　 ） 51. Scientists show the dogs colours ____________.

　　 A. to tell them to eat　　　　 B. to find out if they can see black and white things

　　 C. for fun　　　　　　　　 D. to find out if they can see colours

（　 ） 52. The dogs get ready to eat when they ____________.

　　 A. hear different pieces of music　　　 B. see the monkeys

C. see black things　　　　　　　　 D. see all the colours

（　 ）53. Colours are _____________.

A. all the same to monkeys　　　　　　　　 B. not all the same to dogs

　　 C. different to dogs D. not all the same to monkeys

（　 ）54. If we put food in a blue box and do this every day, a monkey will always go to ____________.

A. the red box to get food　　　　 B. the blue box and put food in it

C. the blue box to get food 　D. the red box and put food in it

（　 ）55. Which of the following is TRUE?　

A. Scientists find that dogs don’t like colours.

B. Dogs like to hear different pieces of music.

C. Monkeys like the food in the box.

D. Monkeys will not go to the blue box if we don’t show them before