A teacher wants to compare scores on a geology exam for two classes. The difference between the sample means is 21.4. If the standard deviation of the distribution of the difference between sample means is 16.66, and she is testing the hypothesis at the 68% confidence level, which statement is true?

A. The difference between the two means is significant, so the null hypothesis must be accepted.
B. The difference between the two means is not significant, so the alternative hypothesis must be rejected.
C. The difference between the two means is not significant, so the null hypothesis must be rejected.
D. The difference between the two means is not significant, so the alternative hypothesis must be accepted.
E.
The difference between the two means is significant, so the alternative hypothesis must be accepted.