They _____ very busy last month. [ ]
A. are
B. were
C. be
D. have been
答案:B
口腔结核病损最常见的形式为
A.结核初疱B.结核性溃疡C.结核性骨髓炎D.寻常狼疮E.硬化性肉芽肿
可以检查受压元件中焊接接头的穿透性缺陷和结构强度的检验方法是( )。
A.渗透检验
B.着色检验
C.耐压试验
D.冲击试验