Question

the use of interchangeable parts in the early 1800s led to -
an increase in production levels
a decrease in immigration
a decrease in free trade between nations
an increase in government regulation of businesses

Explanation:

The use of interchangeable parts in the early 1800s was a key innovation in manufacturing. It allowed for more efficient production, which led to an increase in production levels. A decrease in immigration, a decrease in free trade between nations, or an increase in government regulation of businesses are not directly related to the impact of interchangeable parts, which focused on manufacturing efficiency and output.

Answer:

an increase in production levels