In the mid 1800s, the specific network of route and safe house use by people ecaping slavery was know as

underground railroad

Explanation:

The Underground Railroad.

Explanation:

It was well-known -- well, as well known as it can be since it's was sort of a secret -- throughout the African-American slaves in the 19th century. The Underground Railroad was used as a means to escape from slavery in the South into free states and Canada.

levels of production can be increased by technology while holding labor and capital constant, because increased technology makes the production process more efficient. subsequently, the lras curve is almost a vertical line, that can shift to the right, with an increase in technology.

the relationship between the lras curve and the ppc is that both can make the economy could grow. the ppc achieves that when it shifts outward because of more resources or technological advances while the lras curve shifts if more resources are developed or if there are technological advances.

the lras curve is a vertical line at an output level that represents the number of goods and services a nation can produce over a sustained period using all of its productive resources as efficiently as possible with all of the current technology available to it.

the production possibilities frontier (ppf) is a graphical device that is used for economic analysis of production decisions because the ppf measures the maximum possible combinations of two goods that an economy is capable of producing with its currently available resources and technology.