关于热传递的下列叙述中正确的是：（ ）
A．热量总是从内能大的物体传给内能少的物体
B．热量总是从分子平均动能大的物体传给分子平均动能小的物体
C．热传递的实质是物体间的内能的转移而能的形式不发生变化
D．只有通过热传递的方式,才能使物体的温度发生变化
BC
热传递是改变物体内能的一种方式，热量总是从温度高的物体传递到温度低的物体，而温度是分子平均动能的标志，可以分析解决本题。
| 完形填空。 | ||||
| One day little Johnny went to visit his grandparents on their farm. He was given a slingshot (弹弓) to play with. He practiced in the woods, but he could 1 hit the target (靶子). 2 he got discouraged (气馁), he went back for lunch. As he was walking back, he saw Grandma's pet duck. 3 thinking, he took out the 4 , shot the duck in the head and 5 it. He knew Grandma loved that duck. She would be very 6 if she knew the truth, he thought. Then he hid the dead duck in the wood pile (堆), only to see his sister Sally 7 . She had seen it all, but she said 8 . After lunch Grandma said, "Sally, let's wash the dishes." But Sally said, "Grandma, Johnny told me he wanted to help in the 9 today, didn't you, Johnny?" And then she whispered to him, "Remember the duck?" So Johnny did the dishes. Later Grandpa asked 10 the children wanted to go fishing and Grandma said, "I'm sorry, but I need Sally to help me make supper." But Sally 11 and said, "Well, Johnny told me he wanted to help you." And then she whispered again, "Remember the duck?" So Sally went fishing and Johnny had to 12 at home. After several days of Johnny doing 13 his work and Sally's, he finally 14 stand (忍受) it any longer. He came to Grandma and said what he had done. Grandma said, "Johnny, I know. You see, I was standing at the window and I saw the whole thing. But because I love you, I 15 you. I was just wondering how long you would let Sally make a slave (奴隶) of you." | ||||
|