Out of 12 chocolate bars only 4 of them are chosen, which means 8 of them are not selected at a time.

So to find the required answer we have to evaluate how many ways we can fill the 4 bars of chocolate around the spaces of the un selected chocolate bars. There are 9 such spaces so the required answer is

9C4 = 126. ie., there are 126 ways that the chocolate bars can be selected such that no 2 bars are next to each other