Final answer:
The steel industry with its advancements in steel production was integral in making railroad production more efficient by providing sturdier and inexpensive steel for heavier rail lines.The correct answer is option A
Step-by-step explanation:
The industry that helped make railroad production more efficient is steel manufacturing. Improvements in steel production resulted in the availability of rust-resistant steel that was less expensive and could be used to manufacture more robust and heavier rail lines.
These rail lines could then support heavier locomotives that carried heavier loads, which allowed for expanded railroads across the United States and Europe, transporting more freight and passengers. Not only did this foster a significant expansion of the railroad network itself.
But it also led to greater efficiency in the movement of resources, goods, and people, feeding into the wider industrial expansion of the era.The correct answer is option A