How did electricity change where factories were located

Early mills had run successfully with water power, but by using a steam engine a factory could be located anywhere, not just close to a water source. ... Water power varied with the seasons and was not always available.

d: social contract theory

increases in demand are shown by a shift to the right in the demand curve. this could be caused by a number of factors, including a rise in income, a rise in the price of a substitute or a fall in the price of a complement.

which the answer is:

b