化学介质的毒性危害程度是以国家有关标准规定的指标为基础进行分级，高度危害（Ⅱ级）的最

--What a beautiful school!

–Yes. Many trees ________ in our school every year.

A．plant

B．are planted

C．were planted

D．is planted

Mrs. Weng came back from France in 2010. She _________ there for four years.

A. works B. worked C. has worked

建筑物雨篷结构的外边线至外墙结构外边线的宽度超过（）m者，应按雨篷结构板水平投影面积的1/2计算。

A．2.10

B．2.20

C．2.30

D．2.40

简述纯圆球形贮罐中足球型球罐的结构？

货币制度最基本的内容是规定( )。

A．货币材料
B．货币名称
C．货币单位
D．价格标准