直径是6厘米．
3.14×6=18.84（厘米），
答：直径为6厘米的圆的周长是18.84厘米．
关于消化道出血粪便检查的叙述，正确的是（）
A.消化道出血粪便外观检查就可以检出
B.胃溃疡患者的隐血阳性率可达到55%～77%
C.鲜红色血便可为小肠下段出血
D.溃疡性结肠炎常为黏液性血便
E.过敏性结肠炎常为黏液性脓血便
Look at the factory! It _______ before I came here. [ ]
A. is built
B. has built
C. was built
D. was building
