十二指肠水平段位于()
A．肠系膜上动脉上方
B．肠系膜上动脉前方
C．肠系膜上动脉后方
D．下腔静脉后方
E．腹腔动脉后方
参考答案：C
It is required that under no circumstances ______ betray ourselves even if there are temptations like money or beauty.
A．we will
B．should we
C．we
D．we shall
简述电流比相式母线保护的优点。
