The mean mark on a state-administered mathematics exam by a 10th grade class in Smalltown, Wisconsin, was 95%, while the mean mark on the same exam by 10th grade students in the entire state of Wisconsin was reported to be only 78%. This suggests that the mean can be __________.
A:a parameter or a statistic
B: a parameter only a statistic only
C:neither a parameter
D:nor a statistic
