Why was the model t the most successful passenger car?

It was built by the assembly line method of production.

Explanation:

Henry Ford wanted to build both sturdy and cheap cars for the multitudes.

The assembly line method of production allowed him to improve his profit margin and reduce the cost of the vehicle to buyers.

That´s how the Ford Model T was the best-selling vehicle of all time (until 1972), was the first car to reach a million sells and, by then, it accounted for half of all the cars in the world.

just finished this it is b. centrifugal force

c. troops marched forward in close formation against newer, more accurate weapons