What steps happens first when a cavity forms (i will mark as best answer)

These are the steps, which happen when a cavity is forming and causes long term damage:

White spots: When your teeth are at the start of decaying, you'll notice white spots on your teeth. So most of your teeth may be yellow, then you have spots of white.Enamal Decay: At this point, your teeth will start decaying underneath the surface of the tooth.Dentin Decay: Next, acid and anything harmful to your teeth will dissolve your teeth. If decay moves to your dentin, your tooth will start to experience sharp pain.Involvement of The Pulp: At this point, the pulp within your teeth may become infected by bacteria. Abscess Formation: Then, if the infection reaches the top of the tooth. It could cause swelling, and make the chance of you getting other  diseases.Tooth loss: Tooth loss is by far the worst part, by this time your teeth will start falling of due to being severely infected.

If you ever see any of these signs, I advise you too see a dentist. Not seeing a dentist, could have bad affects on your health.

I hope this helps! :)

-LizzyIsTheQueen

You did not show us the image of the burger, but i shall try to answer as best i can.  when purchasing food, always consider the ingredients as well as the person who prepared it. consider if they were hygienic people or not, in case the burger was infected with bacteria. no mortal should place an infected burger into their mouth.   

The answer is either 3 or 4