单项选择题
A. A disease. B. A cause of fatal plague. C. A substance in a flea’s legs. D. The substance that a flea lives on.
A. They were born to be pale. B. They did not like traveling in sunny countries. C. They wanted to be different from the peasants. D. They thought light color was the color of health.
A. It can reduce the number of passenger complaints. B. It can make air travel more entertaining. C. It can cut down the expenses for air travel. D. It can lessen the discomfort caused by air travel.