顾炎武认为：“知封建之所以变而为郡县，则知郡县之敝而将复变。然则将复变而为封建乎？曰：不能。有圣人起，寓封建之意于郡县之中，而天下治矣。”材料表明其主张是（    ）

(B)

    It's Sunday morning. There are many people in the park.and some boys are playing basketball. There are some girls under a big tree. They're singing and dancing. What are those women doing? They are drinking tea. Look at the woman in a blue coat. Who's she? She's my mother. She is talking to Lin Feng. Lin Feng is her student. He is a good student．He studies hard．He's good at all the subjects. And he's friendly to all his teachers and his friends.

汽车与水平路面的动摩擦因数μ=0.2，当汽车在半径为R=200m的弯道上转弯不打滑时，行驶的最大速率为多少？（滑动摩擦力等于最大静摩擦力）

①转动粗准焦螺旋  ②调节光圈    ③转动细准焦螺旋

④转动转换器      ⑤移动标本