----- Why don’t you do some shopping in the second-hand store ?

------ Well, the goods there are _____, but _____.

A．more expensive; worse

B．more expensive; not as bad

C．cheaper; good enough

D．cheaper; not as good

粉煤灰的均匀性试验以细度为考核依据，单一样品的细度不应超过前（）个样品细度平均值的最大偏差。

A.5

B.10

C.20

D.50