Which strategy fight infections in the body?
exercising at least three times a week
eating food with proper nutrients
taking the daily recommended dose of magnesium
getting enough vitamin d through moderate sun exposure

I believe the correct answer from the choices listed above is the second option. The strategy that would help fight infections in the body would be eating food with proper nutrients since it would strengthen the body's immune system. 
Hope this answers the question. Have a nice day.

By placing 2 fingers at the sternum (the spot where the lower ribs meet) the put the heel of your other hand next to your fingers. hope this