When you are doing an equation like this, multiply every variable by the next. For example, if you had how many ways could 5 colors be arranged, you would do 5 times 4 times 3 times 2 times 1, because there are 5 options for space 1, 4 for space 2 and so on. For this equation, the first coin you toss has 2 possible options, and so do the other 3 coins. So 2 times 2 times 2 times 2 = 16. The answer is A. I hope this helped! Please give brainliest!