An ant(蚂蚁)was drinking at a small river and fell in. She tried her best to reach the side, but she couldn’t move at all. The poor ant got too tired but was still doing her best when a big bird saw her. What a luck! The bird threw a piece of wood in the water. With it the ant reached the bank again. While she was resting and drying herself in the grass, she heard a man coming up. He was walking without shoes on his feet and with a gun(枪)in his hand. As soon as he saw the bird, he wanted to kill her, and he would certainly do so, but the ant bite(咬)him on one of his feet and at the moment the bird flew away at once.
小题1:What happened to the ant?
A．She fell in the water
B．She wanted to swim
C．She was thirsty
D．She was eating小题2:What did the ant want to do in the water?
A．She wanted to look for something
B．She wanted to swim to the bank
C．She wanted to catch a fish
D．She wanted to drink some water小题3:Who helped the ant?
A．A man
B．A fish
C．A bird
D．Herself小题4:What did the man with a gun wear on his feet?
A．A pair of shoes
B．A pair of socks
C．Nothing
D．Some clothes小题5:The man couldn’t kill the bird, Why?
A．He couldn’t see the bird clearly
B．He couldn’t use the gun
C．He didn’t like to hurt the bird
D．His foot was bitten by the ant.
，水平向左
，水平向左
，水平向左
，向右；由于a点的合场强为零，故中均匀薄板在a点产生的场强也等于