To my knowledge, the correct answer among all of the given choices is C.) Steam. If I'm not mistaken, this was the time that more trains came into use.
I hope this is the answer you were looking for and that it helps!! :)
Answer:C
Explanation:I am leaning towards C the most.
A. Iraq was responsible for the terrorist attacks of September 11,2001
It publicized the jobs need to fill in in order to help win the war and keep our economy going