Answer: B) All teenagers.
Explanation:
In statistical survey , a population is a large group of individuals that share some similar characteristics according to the researchers's point of view or the demand of the study.
When the population very large , then he take a sample of population that represents the whole population.
For example : If a researcher wants know the average weight of women in the university , he will need the data of all women in university which is the population for this study.
As per given : A national polling organization wants to estimate the percentage of all teenagers who believe social security will 'be there' for them.
Here , the population of interest : All teenagers.
Sample : 1500 teenagers
37% : sample proportion of teenagers says that they believe social security will 'be there' for them.
Hence, the correct answer is : B) All teenagers.