Answer:
73% of readers who are satisfied with their lives would be described as a sample statistic.
Explanation:
The right option is D.
A) The population include all the readers of USA today.
B) The sample includes all the readers that answer the poll, wether they answer Yes or No.
C) A population statistic would be the population proportion. It is not mentioned in the text, and it would have to be estimated from the result of the sample.
D) A sample statistic is the proportion of readers that answer affirmatively the poll (p=0.73).