The success of the automobile industry in the 1920s was due to

Mass production and easy credit
Cheap gasoline and low government regulation
Monopolistic practices
Sophisticated advertisement campaigns

Mass production and easy credit.

Explanation:

Before the 1920s, cars were very expensive. In the 1920s, the industry turned to mass production because it was really more profitable to produce millions of financially affordable cars than producing a few thousands for the rich people. Technology advances such as the assembly line and design innovations, plus sales strategy  and easy credit, made this possible. In 1918, only 1 in 13 families owned a car. In 1929, 4 out of 5 families had a car.

both are true, the congress does have the power to create banks, even if this power is not specifically described in the constitution, since there is nothing restricting it and there is power given to the congress to make "all laws which shall be necessary and proper". maryland was not allowed to tax a branch of the national bank operating there, and the supreme court decided that no state could. both of these topics were discussed in a decision of the mcculloch v. maryland case in 1819.

this isn't a question and if you're going to list things be kind and use commas.