Cats Live for 14 Years, on Average, with a Standard

Multiple Choice

Cats live for 14 years, on average, with a standard deviation of 2 years. A simple random sample of 78 recently deceased cats is selected, and the sample mean age at death x̄ of these cats is computed. We know the random variable x̄ has an approximately Normal distribution, but why?

A) The law of large numbers
B) The fact that probability is the long-run proportion of times an event occurs
C) The 68-95-99.7 rule
D) The central limit theorem