The answer to the question is (D) it is easier than traditional college classes.
A dual enrollment refers to a situation where high school students are allowed to take courses that are normally intended for college or university-level students together with their high school coursework.
Just because the student is taking the class during her or his high school education, does not mean that the college coursework that they take is easier than it normally is in college – the level of difficulty should be the same.