Which sentence in the passage could be considered a call to action?

a. for children as well as grown-ups, including vitamins and minerals in the daily diet is necessary for enjoying a healthy and long life.
unfortunately, most people don't get enough nutrients from their diets.
b. many people say that the popularity of junk food is the reason why most people are undernourished. this belief is probably partially true. but even people who don’t eat junk food every day still have a hard time getting all the nutrients they need from their food. that’s because they aren’t eating organic food. food that is not organic is treated with pesticides and other chemicals. not only is this food lower in vitamins than organic food, it might also be slightly poisonous.
c. the good news is that there are farmers who refuse to use harmful sprays on their farms. organic farming involves the use of nature-friendly farming techniques and products.
d. so make a healthy choice and switch to organic food to heal, nurture, and protect your body.