A:has gone; has been
B:went, has been
C:goes; was
D:has gone; will be
在反应A+3B═2C+3D中,已知A和B的相对分子质量之比为5:6,2.5g A与一定量的B恰好完全反应,生成3.5g D,则反应中B和C的质量比为( )
Change your water heater, ____ you ____ ____ ____ too much harmful gas.