There are robots all around us. Some do very complicated jobs like flying airplanes and driving subway trains. and some do one simple job. When an automatic washing machine is switched on, water pours in. The machine waits until the water is warm enough for washing clothes. It does this by "feedback" . Information about what is happening is feedback into the robot to tell what to do next. Our eyes, ears and other senses are our feedback. They tell us what is going on around us. So robots are like human beings in two ways. They work and they have feedback. In some ways robots are better than human beings. They work quickly and do not make mistakes. They do not get bored doing the same job over and over again. And they never get tired. So robots are very useful in factories. They can be taught to do many different jobs. First their electronic brain must be shown how the job is done. A person moves the robot's "arms" and "hands" through each part of the job. The most intelligent robots can move and see. Their eyes are cameras. Their fingers can feel shapes and sizes of the objects. These robots have computer brains linked to their eyes and fingers, which control their actions. The expensive robots are used in scientific research. They do such job as handling radioactive materials. The robots used for scientific research   _  .
are not very clever are very cheap are very big are very costly
Question: There are robots all around us. Some do very complicated jobs like flying airplanes and driving subway trains. and some do one simple job. When an automatic washing machine is switched on, water pours in. The machine waits until the water is warm enough for washing clothes. It does this by "feedback" . Information about what is happening is feedback into the robot to tell what to do next. Our eyes, ears and other senses are our feedback. They tell us what is going on around us. So robots are like human beings in two ways. They work and they have feedback. In some ways robots are better than human beings. They work quickly and do not make mistakes. They do not get bored doing the same job over and over again. And they never get tired. So robots are very useful in factories. They can be taught to do many different jobs. First their electronic brain must be shown how the job is done. A person moves the robot's "arms" and "hands" through each part of the job. The most intelligent robots can move and see. Their eyes are cameras. Their fingers can feel shapes and sizes of the objects. These robots have computer brains linked to their eyes and fingers, which control their actions. The expensive robots are used in scientific research. They do such job as handling radioactive materials. The robots used for scientific research   _  .
A. are not very clever
B. are very cheap
C. are very big
D. are very costly
Answer: