起重机械钩头上的缺陷（）焊补。
A、不得
B、可以
C、能
D、同意
参考答案：A
-------Where you ?
------I the teacher’s office.
A．have been; have been to
B．have been to; have gone to
C．have been; have gone to
D．have been to; have been to
并罐式无钟炉顶相对串罐式有哪些缺点？
