压力焊中不包括
A．接触焊
B．超声波焊
C．气压焊
D．电弧焊
E．冷压焊
参考答案：D
简述一般性行业分类。
______nature reserves _______us learn more about protecting animals.
A．Studying ; help
B．Studies ; helps
C．To study; helping
D．Studying; helps
