Answer:
Because people did not know that yellow fever was caused by the bite of an infected mosquito, they assumed incorrectly that people could catch the disease through touch. To help control the disease, letters were cleaned with vinegar before being sent. This did not work, because it was a false cause-and-effect relationship.
Usually, in a conclusion, you wrap up what you have been writing about the whole time. So, a conclusion is basically a summary of the whole text. You can introduce new ideas for the reader, but it is usually inadvisable. In a couple of sentences, you should finish your text, referring to the previous paragraphs and just wrap it all up nicely.
Answer:
its A it flows better then and now
Explanation: