Answer:
Option (a).
Step-by-step explanation:
The upper respiratory infections are mainly caused by the virus and bacteria. These infections are most common in winters. The symptoms of upper respiratory infections are sneezing, cough, cold and fever.
Mariah is a swimmer and she has the chances to experience the more upper respiratory illness. The causative agents of this illness is most likely to enter in the body by water. The swimmers remains mostly in water and the water conditions increases the chances and symptoms of the upper respiratory illness.
Thus, the correct answer is option (a).