冠状动脉起自()
A.冠状窦
B.升主动脉
C.主动脉弓
D.胸主动脉
E.肺动脉
参考答案:B
镁燃料电池以镁合金作为电池的一极,另一极充入过氧化氢,电解质溶液是
酸化的氯化钠溶液,放电时总反应为Mg+2H++H2O2=Mg2++ 2H2O。关于该电池说法正确的是( )
A.镁合金作为电池的负极,发生还原反应
B.放电时H2O2在正极得电子,被还原
C.负极反应式为:Mg-2e-=Mg2+
D.放电时正极附近溶液酸性增强
We are taught that a business letter should be written in a formal style ____ in a personal one. [ ]
A. rather than
B. other than
C. better than
D. less than