The speaker mentioned all of the following as effects of mass transportation on cities EXCEPT a. Growth in city area. b. Separation of commercial and residential areas. c. Changes in life in the inner city. d. Increased standards of living.

毒品的危害性主要表现在（）。

A、毁灭自己

B、祸及家庭

C、危害社会

D、损害国家