胃溃疡的主要X线表现是（）
A.黏膜破坏
B.黏膜中断
C.龛影
D.充盈缺损
E.痉挛性切迹
参考答案：C
She showed the visitors around the museum，the construction _______ had taken more than three years.[ ]
A．for which
B．with which
C．of which
D．to which
表达式operator + (x，y)还可以表示为【 】。
