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.
<em>the process by which green plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.</em>
