消化性溃疡的发病因素中最主要的是()
A.幽门螺旋菌
B.非甾体类消炎药
C.胃酸
D.前列腺素缺乏
E.胃蛋白酶
参考答案:C
There is ________ in his words.We should have a try. (2011·四川,3)
A.something
B.anything
C.nothing
D.everything
I often practice _________ football on Friday.
A.playing
B.to playing
C.play
D.to play