硝酸酯类舒张血管的机制是：
A.直接作用于血管平滑肌
B.阻断α受体
C.阻滞Ca2+通道
D.释放一氧化氮
参考答案：D
14．After a short rest, he came back to he had stopped and continued reading.
A．where
B．which
C．in which
D．that
混床再生步骤？
