Hello!
The flu is spread by pathogens through physical transfer.
Brushing and flossing your teeth will prevent cavities but not the flu.
Fevers are not usually caused by the flu, so reducing it will not prevent it.
The flu is not spread through food, but you should still wash your food to keep it fresh.
Your flu could be spread to someone through and uncovered cough, so the answer is A.
Hope this helps!