Answer:
C. a cross-sectional study.
Step-by-step explanation:
A cross-sectional study -
It refers to the observational study , where a single point is considered at a particular time period from the crowd , is referred to as a cross - sectional study .
It is also known as prevalence study , transverse study and cross-sectional analysis .
Hence, from the given scenario of the question,
Professor Juarez is conducting a cross - sectional study .