The Average Age of Trees in a Large Local Park

Multiple Choice

The average age of trees in a large local park is 60 years, with a standard deviation of 2.2 years. A simple random sample of 400 trees is selected, and the sample mean age x̄ of these trees is computed. We know the random variable x̄ has an approximately Normal distribution, but why?

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