Answer:
a. Cross-sectional study
Step-by-step explanation:
Cross-sectional study -
It is the method to study , a group of people belonging to various subgroups or varieties , against a particular subject , is known as cross - sectional study .
Similarly in the question ,
The survey was done for the disease cholera , ad three groups of people are involved in that .
Hence , from the question ,
The correct term for the given statement is Cross - sectional study .