In 1793, 5,000 people in Philadelphia died of yellow fever in three months. Based on this text, many deaths would have been prevented if people had
A spent more time outdoors in warm weather.
B tried to cure the disease by washing their feet.
C washed their hands more often with soap.
D known the disease was carried by mosquitoes.
The correct answer is D: known the disease was carried by mosquitoes.
Explanation: If people had understood that yellow fever was transmitted by mosquitoes, they could have taken preventive measures, such as reducing mosquito populations and protecting themselves from bites, which could have significantly reduced the number of deaths.