1立方米混凝土中,其各组成成分的质量比为水泥:砂:石子:水泥=324:646:1255:175,其砂率为( )
A: 646/(324+646+1255+175)
B: (646+1255)/(324+646+1255+175)
C: 646/(646+1255)
D: 346/1255
A: 646/(324+646+1255+175)
B: (646+1255)/(324+646+1255+175)
C: 646/(646+1255)
D: 346/1255
