可引起视网膜中央动脉阻塞的是（）。
A.动脉粥样硬化
B.动脉中层硬化
C.老年退化性硬化
D.小动脉硬化
E.废用性动脉硬化
参考答案：A
Directions:
The following picture stands for Chinese Young Volunteers. Write an essay of 160～200 words based on this sign. Your composition should include.
1) description of the sign;
2) reasons why people want to volunteer, and
3) your comments.
四肢截瘫是由于损伤了
A．颈段脊髓
B．胸段脊髓
C．腰段脊髓
D．骶段脊髓
E．尾段脊髓
