Easy answer: A.
Explanation: You can represent the interest rate of 8% as 1.08 (each year you have 108% of what you had last year). Now that you have he interest rate as a number you can do one of two things.
Easy way: 850 (starting amount) * 1.08^5 =1248.93. 5 is the years the interest is applied, so if your money was gaining interest for 8 years it would be 1.08 to the power of 8.
Hard way: Multiply 850 by 1.08, then multiply the answer by 1.08, then the next answer by 1.08, and so on.