1. The illness isn't specified, so let us assume that one of the tennis players or one of the ball boys has a cold during the game.
Sonali could have picked up the pathogen through the tennis ball or through shaking hands with one of the players.
2. Three of the many possible ways to keep ourselves healthy is through the following: Doing regular exercise, eating a balanced diet, and keeping a personal hygiene.
3. Yes. If she had washed her hands frequently or used an alcohol after every game, she could have prevented getting sick.