4. For each ton of pig iron produced in a blast furnace, the amount of ore used is approximately.
A. 2 tons
B. 13 tons
C. 1 ton
D. 5 tons
4. For each ton of pig iron produced in a blast furnace, the amount of ore used is approximately.
A. 2 tons
B. 13 tons
C. 1 ton
D. 5 tons