A study was designed to investigate the effects of two variables(1) a student's level of mathematical anxiety and (2) teaching methodon a student's achievement in a mathematics course. Students who had a low level of mathematical anxiety were taught using the traditional expository method. These students obtained a mean score of260with a standard deviation of50on a standardized test. Assuming a mound-shaped and symmetric distribution, what percentage of scores exceeded160?

A: approximately 100%

B: approximately 84%

C: approximately 95%

D: approximately 97.5%