Read the passage from The American Plague. The reemergence of the deadly disease did not stop people from returning to the city. It did, however, leave a lingering sense of helplessness. Well into December, individuals were still succumbing to the fever, and Thomas Jefferson was worrying over which houses were safe to enter. "Yellow fever," he predicted, "will discourage the growth of great cities in the nation."

The central idea of the passage is that

Jefferson was worried about which houses were safe.
the nation was growing.
the plague still worried people as winter approached.
people came back to the city.

She took up a scalpel and slit the monkey's abdomen, making a slow and gentle cut, keeping the blade well away from her gloved fingers. the spleen was puffed up and tough, leathery, like a globe of smoked salami. she did not see any bloody lesions inside this monkey. she had expected that the monkey's interior would be a lake of blood, but no, this monkey looked all right, it had not bled into itself. if the animal had died of ebola, this was not a clear case. she opened up the intestine. there was no blood inside it. the gut looked okay. then she examined the stomach. there she found a ring of bleeding spots at the junction between the stomach and the small intestine. this could be a sign of ebola, but it was not a clear sign. it could also be a sign of simian fever, not ebola. therefore, she could not confirm the presence of ebola virus in this animal based on a visual inspection of the internal organs during necropsy.