动物的行为多种多样．下列各行为中属于先天性行为的是（ ） A．小狗钻火圈 B．听

改写后的课文内容填空（共10个空，每空1分，满分10分）

Many people believe that “It is always calm before a storm.” Actually it is not true. Before the Tangshan earthquake, strange things happened. Some animals were too n______小题1: to eat and the water pipes in some buildings cracked and b______小题2:. At 3:42 a.m. the terrible earthquake broke out. In fifteen seconds, a large city lay in r_____小题3:. The suffering of the people was e_______小题4:. Almost everything was d_____小题5: and thousands of children were left homeless. Before people could r_______小题6:from the first quake, a second one hit the city. Some rescue workers and doctors were t________小题7:underground. Water, food, and e_______小题8:were cut off. People began to wonder how long the d____小题9: would last.

L_____小题10:， people all over the nation offered the helping hand. With the joint efforts, the city began to breathe again.

单人施工人工呼吸和胸外心脏挤压时，按压次数和吹气次数的比例为（）。

A、5：1

B、15：2

C、30：2

PLC接地线与机器的接地端相连，基本单元必须接地，如果选用扩展单元，其接地点应与基本单元的（）接在一起。

起重机的电气设备必须保证（），在紧急情况下能切断电源安全停车。

A、高效性

B、传动性能准确可靠、控制性能准确可靠

C、较高的电压

D、较低的温度

E、较小电流

F、外部干净

G、表面干燥

H、漆膜无脱落

I、绝缘电阻大

J、接地电阻小

B737NG22CH0007对于主偏航阻尼，需要的SMYD是（）

A.SMYD1

B.SMYD2

C.SMYD1和SMYD2

D.任何一个SMYD