Answer:
Option D is correct.
A voluntary response error was made in this design. This type of sampling only targets those who are passionate about a specific act and call in to vote; it is not a good representation of the population.
Explanation:
When humans are given the choice whether to participate in a survey like in this question, most often than not, the survey becomes biased.
This is because only the people or set of people who feel strongly the most about the subject matter of the poll will participate in the survey. This favours the group that disagrees as this group, if given the choice to express their opinion, will most likely be the set of people that will readily express their discontent.
Discontent is more visibly and strongly expressed in humans.
In order to remove this bias, people should have been chosen at random and their responses recorded.
Hope this Helps!!!