what are the three keys ways to keep your ears healthy monitor the noise level to visit your doctor if you experience any hearing problems and

The correct answer would be the fourth option - wash your outer ears with a warm wash cloth and then dry it with a towel.
It's not the first option because telling your friends to turn their music down would fall under monitoring the noise level. Using headphones is fine as long as you regularly clean them and don't have your music to loud so it's not that option. Using cotton swabs to clean earwax is actually not recommended as you aren't supposed to put anything in your ears as you can cause damage. Therefore it must be the last option. You should clean your outer ears as you can get infections in the outer ear as well as the inner ear. Make sure you dry them properly too.