题目内容:
What is a by-product of burned coal?
A. Aluminum, silicon, and magnetic.
B. Paving material.
C. Fly ash.
D. Concrete additive.
参考答案:
What is a by-product of burned coal?
A. Aluminum, silicon, and magnetic.
B. Paving material.
C. Fly ash.
D. Concrete additive.