Whatisaby-productofburnedcoal?
A.Aluminum,silicon,andmagnetic.
B.Pavingmaterial.
C.Flyash.
D.Concreteadditive.
正确答案:C答案为C。根据题干找到第一段第三句,twokindsofashby-productareproduced:aheavybottomashandafine-as-powderflyash符合题意。

Whatisaby-productofburnedcoal?
A.Aluminum,silicon,andmagnetic.
B.Pavingmaterial.
C.Flyash.
D.Concreteadditive.
正确答案:C上一篇 [A] power[B] authority[C] ability[D] right
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