75kg/m钢轨的螺孔中心至轨底距离最接近的是()。
A、79mm
B、80mm
C、78mm
D、81mm
参考答案:B
Though young, he succeeded in taking the machine skillfully and then put it together without any difficulty.
A.out
B.down
C.apart
D.up
呕血的常见病因是()。
A.消化性溃疡
B.食管静脉曲张破裂出血
C.胃癌
D.急性胃粘膜病变
E.急性出血性胃炎