阅读短文, 选出正确答案。

（A）

   A picture is on my desk. It is a picture of Mary's family. The man is her father Mr. White. He is a doctor. A woman is behind Mary. She is her mother. She's a teacher. A boy is in the picture, too. He is Mary's brother, Sam. Mary and Sam are in the same school. But they aren't in the same grade. They look like their mother. The White family are English. They come from London.

唐朝实行的行政制度是（    ）

（1）在图1中，标出磁感线的方向．

（2）图2中0B是一条反射光线，ON为法线．请在图中画出相应的入射光线．

（3）请在图3中画出经过透镜折射后的光线．

spring     summer  ____

如图，Rt△ABC中，∠C=90°，∠A=30°，AB=4，将△ABC绕点B按顺时针方向转动一个角到△A′BC′的位置，使点A、B、C′在同一条直线上，则图中阴影部分的周长是（　　）