月球上含有丰富的32He．下列关于32He的说法不正确的是（） _爱下问搜题

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问题选择题

月球上含有丰富的

3

2

He．下列关于

3

2

He的说法不正确的是（　　）

A．是一种核素

B．原子核内有l个中子

C．与

4

2

He互为同位素

D．比

4

2He少一个电子

答案

A、₂³He和₂⁴He是氦元素的两个核素，故A正确；

B、₂³He的中子数=3-2=1，故B正确；

C、₂³He和₂⁴He质子数相同，中子数不同，故互为同位素，故C正确；

D、₂³He和₂⁴He质子数相同，核外电子数相同，故D错误；

故选：D；

完形填空

完形填空。
It was a cold winter afternoon. Robert stopped for a moment as he crossed the bridge and looked down at the river below. There were hardly any 1 on the river. Near the bridge, however, almost direct below, 2 was a small canoe (独木舟), with a boy in it. The boy was wearing 3 and shivering (颤抖) with cold, Robert noticed. Just then he heard a cry, “Help! Help!” The cry 4 from the river. Robert looked down. The boy was 5 the water and his canoe was floating away. “Help! Help!” he called again. Robert was a good 6 . Taking off his clothes, he 7 into the river. The 8 water made him tremble（颤抖） all over, 9 in a few seconds he reached the boy. “Don’t be afraid,” he said and started to swim towards the river bank, 10 the boy with him. But at that 11 he noticed a large motor boat under the bridge. There were several people on the boat, all 12 in his direction. Robert 13 to swim towards the boat. “Give me a hand,” he shouted 14 he got near the boat. He 15 up into a row of faces. “It’s funny,” he thought. “They look so 16 .” Silently they helped the boy into the boat and 17 him in a blanket (毯子). But they did not move to 18 Robert. “Aren’t you going to pull me 19 , too?” “You!” said one of the men. Robert noticed that he was standing next to a large 20 . “You! Why, we were making a film and you spoiled (破坏) a whole afternoon’s work! You can stay in the water!”
( )1.A. fish ( )2.A. there ( )3.A. more ( )4.A. happened ( )5.A. on ( )6.A. swimmer ( )7.A. threw ( )8.A. deep ( )9.A. but ( )10.A. pushing ( )11.A. place ( )12.A. seeing ( )13.A. decided ( )14.A. while ( )15.A. turned ( )16.A. nervous ( )17.A. wrapped ( )18.A. save ( )19.A. on ( )20 A. boat	B. boats B. it B. many B. went B. within B. guard B. looked B. cool B. so B. dragging B. period B. smiling B. went B. till B. looked B. afraid B. left B. thank B. out B. blanket	C. waves C. where C. much C. arrived C. in C. soldier C. jumped C. dirty C. and C. holding C. second C. looking C. agreed C. for C. hurried C. excited C. placed C. wrap C. away C. camera	D. birds D. that D. little D. came D. under D. player D. turned D. cold D. or D. catching D. moment D. shouting D. promised D. as D. stood D. angry D. threw D. help D. off D. screen

名词解释

沉积盆地