Each month, the census bureau mails survey forms to 250,000 households asking questions about the people living in the household and about such things as motor vehicles and housing costs. Telephone calls are made to households that don’t return the form. In one month, responses were obtained from 240,000 of the households contacted. If the household does not return the form, and cannot be contacted by telephone:___________
a. the residents in the suburb that support the new recreation center.
b. the 250,000 households contacted.
c. only U.S. households with phones.
d. all U.S. households.

The concept of population census is applied in solving the question. Population as we know is the total number of inhabitants in a place or the combination of people dwelling in a place.

Sample is a unit or a part of population census and not the entirety of the population.

In this case, Our population of interest is the whole inhabitant in the country, as indicated that census bureau mails survey form to 250,000 households asking about some question. And In one month, responses were obtained from 240,000 of the households contacted.

As it is, our population of interest is not the household that can be contacted by telephone because it is presumed that the households with phones may be lesser than the total population of the sample been considered. Irrespective of those that were or were not contacted by telephones, our population of interest is ALL OF US HOUSEHOLDS. As the essence of a survey is to have an idea of an estimate of the population parameter.

Hence the correct option is D