问题
单项选择题
正弦交流电的三要素（）。
A.电压、电动势、电能
B.最大值、角频率、初相角
C.最大值、有效值、瞬时值
D.有效值、周期、初始值
答案
参考答案：B
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正弦交流电的三要素（）。
A.电压、电动势、电能
B.最大值、角频率、初相角
C.最大值、有效值、瞬时值
D.有效值、周期、初始值
参考答案：B
阅读下面短文，从短文后各题的A、B、C、D四个选项中，选出适合填入 对应空白处的最佳选项, 并在答题卡上将该选项涂黑。 My job was to make classroom observations and encourage a training program that would enable students to feel good about themselves and take charge of their lives. Donna was one of the volunteer teachers who participated in this . One day, I entered Donna’s classroom, took a seat in the back of the room and . All the students were working a task. The student next to me was filling her page with “I Can’ts.” “I can’t kick the soccer ball.” “I can’t get Debbie to like me.” Her page was half full and she showed no of stopping. I walked down the row and found was writing sentences, describing things they couldn’t do. By this time the activity aroused my , so I decided to check with the teacher to see what was going on I noticed she too was busy writing. “I can’t get John’s mother to come for a parents’ meeting.” I felt it best not to . After another ten minutes, the students were to fold the papers in half and bring them to the front. They placed their “I Can’t” statements into an empty shoebox. Then Donna hers. She put the lid on the box, tucked it under her arm and headed out the door. Students followed the teacher. I followed the students. Halfway down the hallway Donna got a shovel from the tool house, and then marched the students to the farthest corner of the playground. There they began to . The box of “I Can’ts” was placed at the of the hole and then quickly covered with dirt. At this point Donna announced, “Boys and girls, please join hands and your heads.” They quickly formed a circle around the grave. Donna delivered the eulogy (悼词). “Friends, we gathered here today to the memory of ‘I Can’t.’ He is by his brothers and sisters ‘I Can’ and ‘I Will’. May ‘I Can’t’ rest in . Amen!” She turned the students and marched them back into the classroom. They celebrated the of “I Can’t”. Donna cut a large tombstone from paper. She wrote the words “I Can’t” at the top and the date at the bottom, then hung it in the classroom. On those rare occasions when a student and said, “I Can’t,” Donna pointed to the paper tombstone. The student then remembered that “I Can’t” was dead and chose other statement.
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