The group of students is doing a comparative investigation (option A) rather than a descriptive, controlled, or experimental investigation.
What is a comparative investigation?
A comparative investigation is a type of scientific study in which researchers compare different groups or conditions to identify similarities and differences. The goal is to analyze and understand the relationships between variables without necessarily manipulating them.
This occurs in the study presented because the students are comparing two types of surfaces with the same experimental units in this case the earthworms.
Note: Here is the complete question:
A group of students is setting up a test to see whether earthworms prefer rough or smooth surfaces which type of investigation is the group doing A.Comparative B. Descriptive. C. Controlled. D. Experimental