题目

下列物质中，通常情况下全是导体的一组是（ ）A． 金属、盐水、石墨 B． 金属、塑料、橡胶 C． 金属、大地、玻璃 D． 大地、盐水、陶瓷 答案： 根据导体和绝缘体的定义：容易导电的物体是导体，不容易导电的物体是绝缘体即可作出判断． 解答： 解：通常情况下常见的导体包括：人体、大地、各种金属、石墨、酸碱盐的溶液等． A、金属、盐水、石墨都属于导体； B、塑料、橡胶属于绝缘体，金属属于导体； C、金属、大地属于导体，玻璃属小题1: 根据句意及所给中文提示或英文解释，写出句中所缺单词。51. Children in the west usually wear    ▲   (特殊的) costumes with masks at Halloween.52. Zhang Shaohan has a sweet    ▲   (嗓音), and many of us like listening to her songs.53. People around the world love    ▲   (和平)and hate wars.54. As we know,  ▲   (星期一) is the second day of a week.55. Sorry, I didn’t know you. Would you please speak more    ▲   (清楚地)?56. Now we are short of water and we should s  ▲   water in our daily life.57. Peter’s father is very    ▲   (not free), so he does not have much time for his family.小题2: 根据句意，用括号中所给单词的适当形式或句子的语法要求填空。58. My grandpa likes    ▲   (chat) with his friends under the big tree.59. —Would you like some bananas?—No, thanks. I    ▲   (eat) one already.60. The style of this dress is popular, but I don’t like    ▲   (it) colour.61. What a    ▲   (snow) day! The ground is covered with snow everywhere.62. July 1st is our Party’s    ▲   (ninety) birthday this year. We Chinese people are going to celebrate it.63. Beijing is one of    ▲   (beautiful) places in China, and I have been there twice.64.    ▲   (lucky), they escaped from the burning building with the help of the firemen.65. We    ▲   (ask) to help our parents do some housework every day.