Tobias has mononucleosis. Mononucleosis is a disease that tires and weakens the body. It is caused by a contagious virus that is transferred through direct contact. Which would be the best explanation of how Tobias contracted mononucleosis?

Mononucleosis is caused by a contagious virus, so Tobias must have been exposed to the virus rather than inheriting it or getting it from lack of exercise. A contaminated water fountain could transfer the virus through saliva left by an infected person. Therefore, the best explanation is that Tobias drank from the contaminated fountain.

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