According to the 2010 US Census, 24% of us residents are under 18 years old. Suppose we take a random sample of 500 US residents. Let X = the number of people in the sample who are under 18 years old.
Is it appropriate to use a normal distribution to model the sampling distribution of X?

a. Yes because they find a percentage for their data
b. Yes, because np and n(1-p) are both greater than or equal to 10
c. Yes because they randomly sample the population
d. Yes, because the population distribution is normally distributed.