Can you explain and solve this question for me ?

1) The average age of residents in a large residential retirement community is 69 years with standard

deviation 5.8 years. 100 residents are randomly selected, and the sample mean age x of these residents

is to be computed.

a. We know the random variable x has approximately a normal distribution because of

A. the central limit theorem.

B. the law of large numbers.

C. the 689599.7 rule.

D. the population we're sampling from has a Normal distribution.

b. What is the probability that the average age, x , of the 100 residents selected is more than 70

years is