Look at this public service announcement. what is the purpose of this public service announcement? to encourage people to eat healthy meals to encourage people to purchase less food to urge people to keep each food group separate to urge people to eat more meals per day

I think the answer is 
to encourage people to eat healthy meals

is basically a good source of getting and others by what you know for example if someone asked a question and you know the answer you could answer it and get some points or if you need on a question you could make a post about it and wait till someone answers it or just look up the question and see if someone else has asked about it