判断胎儿成熟度，以下哪项价值最高
A．孕妇血清肌酐B．羊水L/S比值C．孕妇血清HPLD．孕妇尿E3E．OCT试验
参考答案：B
某交流发电机给灯泡供电，产生的正弦交变电流的图象如图所示，下列说法正确的是
A．该交变电流的频率为0.02 Hz
B．该交变电流的瞬时值表达式i=5sin 100πt (A)
C．在t=0.01 s时，穿过交流发电机线圈的磁通量最大
D．若发电机线圈的电阻为0.4 Ω，则其产生的热功率为5 W
—Could you tell me _____?
— I'm sorry. The traffic was too heavy. [ ]
A. why were you late for the meeting
B. why you were late for the meeting
C. when you were late for the meeting
