Answer:
When Mr. Eli Shun devising a study that consists of assessing children of different ages at the same time is an example of a cross-sectional research design.
Step-by-step explanation:
In medical science and social science research, a cross-sectional study is a type of observational study in which the designer takes and then analyzes data from a population during a specific moment in time. A cross-sectional survey works as a snapshot of the population the study is recollecting data from. Mr. Eli Shun is studying the development of emotion in children, so he asses the population, in this case children of different ages, at the same time to gather the information he needs for his doctoral dissertation.