上消化道出血最常见病因是（）。
A.食管静脉曲张破裂
B.慢性胃炎
C.消化性溃疡
D.胃癌
E.急性胃炎
参考答案：C
More money __________ when we use both sides of paper. [ ]
A. will save
B. was saved
C. has saved
D. will be saved
