There was a knock at the door. It was the second time someone ______ me that evening.

A．按其3.7%的年增长率，中国80岁以上(含80岁)的人口在2020年将达两千两百万。
B．达80高龄的中国人口每增加3.7%就有2020人加入这支两千两百万的高龄队伍中。
C．按3.7%的增长率计算，80岁或80岁以上的中国人口即将在2020年超过两千两百万。
D．因中国人口增长率达到了3.7%，其中年龄达到80岁的人在2020年将超过两千两百万。
E．3.7%的中国人口已达80高龄，每年还有2020人加入到这支两千两百万的高龄队伍中。

A．pay the price for its 83 million aged people
B．keep its aged population from growing too fast
C．begin building an old-aged social security system
D．look at its own problems as an aged society