正常新生儿呼吸系数为安静时每分钟（）
A.50～60次
B.45次左右
C.30～40次
D.20～30次
E.18～20次
参考答案：B
Choose and write．（选择正确的单词填空。）
1. My legs are __________________ (short, shorter) than my father's.
2. My father's legs are__________________(long, longer),but my legs are short.
3. My mother is__________________(tall, taller) than Lucy.
4. My father is__________________(tall, taller). Her father is short.
为什么几组电流互感器组成的保护装置有一点接地？
