Which innovation enabled ordinary people to buy cars?
a.
j. p.morgan's methods of banking that made it easy to get credit
b.
thomas edison's use of electricity to keep factories open around the clock
c.
henry ford's assembly line, which made cars inexpensive
d.
joseph pultizer's use of advertizing in newspapers

The correct answer is C. The innovation that enabled ordinary people to buy cars was Henry Ford's assembly line, which made cars inexpensive.

Explanation:

Henry Ford was the founder of the Ford Motor Company and the creator of the modern production lines used for mass production.

He is credited with Fordism, a system that spread between the late thirties and early seventies, developed through the manufacture of a large number of low-cost cars through assembly line production. This system involved the use of specialized machinery and a large number of employees with high salaries, and its result was an specialization of the work, which caused that the times and costs of production were reduced. In this way, the cars lowered their sale price, making it accessible to the general public.

c) troops march forward in close formation against newer, more accurate weapons

the answer is c. they believed the royal family should hold all the power.