It is usual in telephone surveys to use random dialing equipment that selects the last four digits of a telephone number at random after being given the land-line exchange (the first three digits; note that cell phone exchanges differ from land-line exchanges). Which of the households will be included in this sampling frame by random digit dialing? a. Households that possess only cellphones Poor households (cannot afford a phone)
b. Households with unlisted numbers
c. Households without telephones
d. Households with land-line telephones that have moved into the community since the most recent community telephone directory was printed.