The answer is: A.through competition between businesses.
According to smith, businesses would always wanted to obtain as money costumers as possible. During the process of competition, they would keep trying to provide the customers with the cheapest price possible. Eventually, the power of supply and demand would bring the price of the product into a fair point.
The answer is B the invention of balance made trade easier
100 years ago use boat, we also use boat now:)
