竞价方式包括( )。
A．集合竞价
B．连续竞价
C．单一竞价
D．整体竞价
参考答案：A,B
She went to the supermarket and ______ what she needed, she returned home, light-hearted.
A．bought
B．having bought
C．buying
D．to have bought
锅炉在什么情况下会遭至氧腐蚀？
