问题补充：
The number of the people who own cars since 1990.
A. is increased
B. are increased
C. have been increasing
D. has been increasing
答案：
A. is increased
B. are increased
C. have been increasing
(答案→)D. has been increasing
解析：考查主谓一致和时态；本题的主语是the number of…指…的数量。定语从句who own cars修饰the people。本句的主语是the number of…指…的数量；该短语做主语时，谓语动词用单数。根据since说明本句使用完成时。句意：自从1990以来拥有汽车的人的数量一直都在增加。故D正确。
