Mary, together with his parents, ______ going to visit Shanghai next month.[ ]

A. was

B.  is

C. were

D. are

利用电流产生的全部热量都集中在一点上，因而金属受热熔化，同时在电极加压下使焊点金属得到焊合的焊接方式是( )。

A．电弧焊

B．电阻定位焊

C．电渣压力焊

D．气压焊