Br2 is the correct answer
When finding the moles in a compound you have to know the grams. In this case, 25.2 grams are given for KMnO4. To find the moles you would divide the amount of grams by the molar mass of KMnO4. The molar mass of KmnO4 is 158.034. You you would now divide 25.2 by 158.034 which is 0.15946 moles. Depending on how many decimal places the questions asks for is dependent on you. I just went with 5 significant figures.