曳引机承重钢梁底座有两种方式，一种是制作混凝土底座，另一种是型钢架起钢梁。
参考答案：对
— Did you have a good weekend?
— . I was busy studying for the test.
A．Sure
B．I think so
C．I am afraid not
D．I hope not
正交相移键控
