Which sentence has a formal style and tone? a) it ain't necessarily true that people who are good at geometry often turn into engineers. b) see, the problem is, you guys just don't know what is causing the water shortage in this city. c) y'all need to study much with much more diligence, if y'all are going to do well on this next test. d) scientists have spent years trying to determine how tsunamis can be predicted with greater accuracy.

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.