A:各个面都是平行四边形的直棱柱
B:对角面是全等矩形的四棱柱
C:侧面都是矩形的直四棱柱
D:底面是矩形的直棱柱
写出地壳中元素含量第二的金属元素:____ .
— There is an art festival in our school on Saturday.
— Oh, great! We'll _________ then.