Question

which type of investigation usually includes a control group?
descriptive investigation
experimental investigation
comparative investigation

Explanation:

In an experimental investigation, a control group is used to compare the effects of a manipulated variable. The control group is not exposed to the independent - variable being tested, while the experimental group is. This helps to determine if the changes observed in the experimental group are due to the independent variable. Descriptive investigations focus on gathering data about a phenomenon without manipulation, and comparative investigations compare different groups or conditions but don't always have a true control group in the same sense as experimental investigations.

Answer:

B. Experimental investigation