Answer: b/autonomous
Explanation: A child has their major decisions (like medicine, or research) taken care of by their parents or the person taking care of them. Autonomous means that you have the ability to make your own decisions and children don't have that in being a research subject. Dependent means under the care of someone so since children meet that description, this doesn't fit. Neither does successful, which isn't a requirement in human research. Healthy doesn't fit as some children are healthy and some are not.