What is the key to proper nutrition?

Eat a variety of foods, even in very small amounts.

Explanation:

Our dietitians recommend eating a variety of colorful fruits and vegetables, whole grains, legumes, lean meats, fish, eggs, nuts, and seeds. A balanced meal contains a protein source, a grain or starchy vegetable, fresh vegetables, and healthy fat.

Hope this helps!

d. planting trees

the trees take in carbon to make oxygen.