Question 281458
a.A normal distribution is any distribution that is not unusual.
  This is not necessarily true; not unusual does not directly mean a "normal distribution".

b.The graph of a normal distribution is bell-shaped.
  By definition, this is true.

c.If a population has a normal distribution, the mean and the median are not equal.
  This may or may not be true; mean and median are different measures of central tendancy.  

d.The graph of a normal distribution is symmetric.
  Again, by definition, this is true.