Spinach is considered a good source of what nutrient?

All of these are correct. Spinach is an extremely nutrient-rich vegetable. It is an excellent source of many vitamins and minerals, including Vitamin A, Vitamin C, Vitamin K1, folic acid, iron, and calcium. Spinach also contains several other vitamins and minerals, including potassium, magnesium, and vitamins B6, B9, and E. Eating spinach has a host of benefits. It may reduce oxidative stress, promote eye health, fight cancer, and regulate blood pressure.

Source: Healthline