Answer a. Estimate a population proportion.
Explanation:
A population proportion denotes a specific attribute of a population measured in percentage, the above analysis is on losing weight by the populace.
A mean only refers to the average of the population without reference to a particular quality.
The analysis is not testing a claim but it's only making reference to earlier findings on the population. A claim would have given us a specific quality which the population has been predicted or established to adhere to.