1) Exercise it by singing and hitting different notes, however don't go overboard
2) Make sure you don't overuse your voice, as well as trying to rest your voice when you are sick
3) Overall, have healthy habits, like not smoking and drinking a sufficient amount of water.
Answer:
exercising excessively,
taking a large amount of laxatives
self-inducing vomiting
Explanation:
There's many options for this but what i have found is the best source for your calcium is yogurt it helps in many ways.
1)30% of your calcium
2)20% of vitamin D
other options-
milk, cheese, eggs, salmon, and spinach