You are Master of a towing vessel engaged in towing three barges astern.The middle barge of the tow would be required to sound which of the following during restricted visibility ().
A. No fog signal
B. A prolonged blast at intervals never to exceed more than two minutes
C. A prolonged blast followed by two short blasts at intervals never to exceed more than two minutes
D. A prolonged blast followed by three short blasts at intervals never to exceed more than one minute
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欧姆定律是反映电路中电压、电流和电阻之间关系的定律,它们的具体的关系是()。
A. 通过导体的电流与加在导体两端的电压成正比;
B. 通过导体的电流与导体的长度成正比;
C. 通过导体的电流与导体的电阻成反比;
D. 它们之间没有联系。
28岁男病人,有急性间歇性血卟啉病,因急性阑尾炎拟行手术治疗。血卟啉病主要缺乏()
A. 维生素A和D
B. 维生素B12
C. 尿卟啉原合成酶
D. 卟吩胆色素原
E. 2,3-二磷酸甘油酸
在Word中,文件菜单中的“新建”命令和“常用”工具栏上“新建”的功能完全一样。()
A. 正确
B. 错误
拉坯是我国陶瓷器生产的传统方法,凡圆器琢器俱用拉坯方法成型。
A. 正确
B. 错误