Answer:
a. longitudinal
Explanation:
A longitudinal study examines a given group over a long period of time, so collecting data from the same group of 30 people over their lifetime certainly fits that definition. It's more like an evolution study.
A cross-sectional compares different groups at the same point in time. So, it's more like a survey.
A microgenetic is much focused in time, providing multiple data sets in a short time to examine rapid evolution of a subject.
An experimental study design will make interactions and experiments with the study group, while this is not the case here apparently, and experimental is usually for a much shorter period than a generation.
Mondays and Thursdays is only 2 days a week. So 2.15x2 is 4.3 hours a week. 4.3x3= 12.9 hours every 3 weeks or 12 hours and 54 minutes
World human population reached one billion
