蝗虫是有名的农业害虫，它进行气体交换的部位是（ ）
A．肺
B．气管
C．气门
D．体表
在蝗虫腹部第一节的两侧，有一对半月形的薄膜，是蝗虫的听觉器官．在左右两侧排列得很整齐的一行小孔，就是气门．从中胸到腹部第8节，每一个体节都有一对气门，共有10对．每个气门都向内连通着气管．在蝗虫体内有粗细不等的纵横相连的气管，气管一再分支，最后由微细的分支与各细胞发生联系，进行呼吸作用．因此，气门是气体出入蝗虫身体的门户．
故选：B
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| Bill, a thirteen-year-old boy, thought he had grown up to be a man. But his parents told him, "You won't be a real man until you begin to 1 helping others." One morning, his parents gave him some money to 2 some milk for them. Outside a shop he saw a homeless old man who looked very 3 . Bill went to him and asked, " What's wrong with you?" The old man answered, " I'm hungry. I haven't had any food for two days." All the thought of his parents' words, Bill said to the old man, "Let's go to the 4 ." When they got there, Bill asked the waiterto bring out bread and coffee to the old man. The old man finished the meal quickly. After the waiter 5 the plate and the cup, the old man said, "Sorry for give you too much 6 . I'm fine now. I'll 7 forget your kindness! You are a very good young man" Bill was 8 when he heard this. Just when he wanted to pay for the meal, the waiter came. Bill and the old man learned 9 that he food was free 10 it was the birthday of the boss, and they were the first customer(顾客) that day. | ||||
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