The cotton gin directly led to an increased demand for

boats

railroads

slaves

tractors

C. Slaves

Explanation:

Plantation owners were starting to figure out how easy the cotton gin was and how much profit they could be making, so they would buy more slaves and grow more cotton. The cotton gin essentially led to an increase in slaves.

abraham lincoln

the lachish letters were written by hoshaiah, a military officer stationed possibly in mareshah,   and sent to yaush, possibly the commanding officer at lachish.

the series of letters were written in carbon ink in ancient hebrew on clay ostraca, shortly before lachish fell to the babylonian army of king nebuchadnezzar in 588/6 bc during the reign of zedekiah, king of judah.