Answer:
d. all registered voters in Texas
Step-by-step explanation:
The method used here was sampling. And the specific sampling method is referred to as the simple random sampling.
It should be understood that, simple random sampling can be explained as a sampling method where a group of subjects considered for study are selected from a larger group.
In this case, the research center has a list of the entire population, and they are randomly selected from that population.
This means that, the selected 1000 phone numbers,[ i.e the sample] will be representative of the population that it was sampled from, this means from all the registered voters in Texas.