Although Whitney Houston died of an accidental drowning on February, 11, adequate evidence

showed that cocaine was a factor that          to her death.[      ]

A. distributed

B. substituted

C. contributed

D. supplemented

观察下图，我国GDP快速增长的主要原因是(　)

A．人民公社化运动

B．加入世界贸易组织

C．城市化速度加快　

D．改革开放