Answer: A. A convenience sample is structured based on accessibility to the researcher, and a voluntary sample is based on participant interest.
The structure of a convenience sample is based on how accessible it is to the researcher while that of a voluntary sample is based on the interest of the participant. In other words, convenience samples are sought for people who are easy to reach while a voluntary sample is only interested in people who voluntarily want to be part of the survey.
A good example of convenience sampling is standing at a park and asking people you find questions on something in order to get their ideas. On the other hand, an example of a voluntary sample is a customer satisfaction survey where businesses ask customers to volunteer their thoughts in getting information. They are both non-probability samples however as the chance of an element of the population being chosen is not known. These samples are biased as they tend to favor some outcomes over others.