A、Shape. B、Color. C、Price. D、Size. D从男士的话语中可知，过去使用的机器是“enormous”(巨大的)，由此可知是尺寸太大的问题，故B选项是正确答案。

A lot of doctors can tell what’s wrong with you by sleeping, and I can do this by smelling. This actually goes back to the day of ancient Greece. For example, you can walk into a room or get close to a patient who had diabetes that is not well controlled. There is a kind of sweetish smell. That means I can walk into a room and tell if a patient has kidney failure or liver failure. And now there is a machine that can do that too. It is fascinating that there have been these machines in the past, but they were just enormous. These machines are impossible to use clinically, because, you know, in a whole room for the equipments. So in the past, they were not used in therapy. But the newly-invented ones are very small and concise. They use new laser technology and now available given the size of the machine. Unlike the previous, they are just of the size of microwave. However, they are very much in the experimental stage. Interesting, unlike any of these things which are produced by commercial company, this work is being done be the federal government.
16. What disease can’t be smelt?
17. What was the problem of the machine in he past?
18. Which of the following statement is true?
19. What stage of the new machine is now?
20. What is the difference about the machines from the past ones?