Answer:
a. It is greater than the mean of the average difference of the population
Explanation:
Given is - Exactly 10% of the students in your sample tended to over report their height more than the average student in the general population at the school.
It is very certain that the sample is biased towards the higher spectrum.
We can say that the real value of the mean is lower than the original value of our sample population.
So, option A is correct.