古希腊、罗马的政治机构中，有公民大会、五百人议事会、元老院、执政官等，我国古代西周出现了宗法制和分封制，这些机构和制度说明的实质问题是

从每小题所给的A、B、C三个选项中，选出可以填入空白处的最佳答案。

    It is the first day for school．All the students are1 in the classroom．Mrs．Green 2 and says，"Good morning，class．I'm your teacher．I'll teach you English，math and some 3 classes．If you have any questions (问题)，you can 4 me．I'm very glad to answer (回答) your questions．Boys and girls，from now on，you are school 5．You must study hard at school and help your parents at home．"

    A boy puts up6 hand and asks，"We'll do well in our lessons．We can be good students．But what can we do to 7 parents at home?"

    The teacher says，"Think it over and you'll 8 the answer．" "Who usually washes your clothes?"

    A girl stands up and says，"The washing machine (洗衣机)!"

    "Who often 9 for you?" asks the teacher．

    "The microwave oven (微波炉)，" says a tall boy．

    "Who uses them?" asks the teacher 10．

    "The electricity (电)!" all the students answer at the same time．