Answer:
It is D
Explanation:
it's correct I did some research on go0gle when you type in the question
A) They made a new improvement spinning and waving the coal on machines
B) it helped by using it power to smelt iron and steel
C)Pump out deepening mines so that more and more power to keep the machines running
Unrestricted submarine warfare, which became prominent in World War I, meant that submarines could sink any time of vessel at any time without warning. Before this, they had to surface first and place crews on lifeboats.
