以下哪种噪声不是根据来源划分的( )。
A. ( 人为噪声
B. ( 自然噪声
C. ( 电路噪声
D. ( 单频噪声
What do the traditional gender roles refer to in the fourth paragraph
A. Women's getting into the paid labor force.
B. Women's stay at home to take care of home and children.
C. Multiple roles a woman plays in soxiety.
D. Social status assigned to a traditional woman.
正确的质子酸HPO2-4的离解反应是( )。
A. ( HPO2-4+H2O=H2PO-4+OH-
B. ( H2PO-4+H2O=HPO2-4+H3O+
C. ( HPO2-4+H2O=PO3-4+H3O+
D. ( HPO2-4+OH-=PO3-4+H2O
硝酸酯类防治心绞痛药的作用机制是
A. 松弛平滑肌
B. 扩张冠状动脉
C. 降低心肌耗氧量
D. 改善左心室顺应性
E. 保护缺血心肌细胞