Read the passage from an argumentative essay.

"The Columbian Exchange was bad. It had many effects on native peoples. One of these effects was disease. Disease harmed people. It led to death. Some say up to 90 percent of native peoples died.”

How should the passage be revised to create a more formal tone?

Slang terms should be removed.
First-person pronouns should be added.
Simple sentences should be balanced with more complex ones.
Long and complex sentences should be split apart and made shorter.