Imagine After Grading This Exam I Look at the Distribution

Multiple Choice

Imagine after grading this exam I look at the distribution of test scores in this class and conclude there is a group of students for whom the material was very difficult and another group of students for whom the material was very easy. Which of the following would MOST likely lead to this conclusion?

A) The distribution is bimodal.
B) The standard deviation is very small.
C) The mean was higher than I expected.
D) The distribution is peaked.