下列土壤孔隙所吸附的土壤水，有效性最高的是（）。
A．非活性孔隙
B．通气孔隙
C．毛管孔隙
D．无效孔隙
参考答案：C
79. Before there goes the bell for class, our math teacher took out a piece of and wrote his problems on the blackboard.
A．brush pen
B．chalk
C．paper
D．Pencil
胃癌的主要X线表现是（）
A.黏膜破坏
B.黏膜中断
C.痉挛性切迹
D.充盈缺损
E.龛影
