在PMCAD中，可以定义的梁截面类型有（）。
A、矩形
B、工字形
C、圆形
D、槽形
E、任意多边形
参考答案：A, B, C, D, E
跟据汉语提示，用适当的单词填空。
1. Our English teacher is very kind. She is ________ (友好) to us students.
2. My house is on a ________ (繁华的) street.
3. Look, the boys ________ (正在读书) under the tree over there.
4. The ________ (叶子) of the tree are yellow.
5. The library is between the restaurant and the ________. (超级市场)
已知圆筒的外径为1500mm，壁厚为20mm，圆筒的展开长度为（）毫米。
A.1500π
B.（1500+20）π
C.（1500-20）π
