Answer: (a) False; (b) False; (c) True;
Explanation: The alternative (a) is false because, in a distribution, its center is not the mean but the median. Although both mean and median means average value, mean is a value calculated as if all the distribution would have the same value; Median is the actual middle centered value of a distribution, that's why it is the Median the value in the center of a distribution;
The alternative (b) is false due to the definition of standard error of the mean: Standard Error of Mean (SEM) is the measurement of how far the mean sample is from the population sample.