The government placed _____ on the numbers of foreign cars that could be imported.

A．limitations

B．restraint

C．requirements

D．restrictions

吗啡激动导水管周围阿片受体（）

A．吗啡镇痛作用是

B．吗啡成瘾性产生是

C．吗啡镇咳作用是

D．吗啡引起瞳孔缩小是

E．吗啡引起情绪变化是