Question

in which of the following do the researchers divide the subjects into groups? observational study controlled experiment survey

Explanation:

In a controlled experiment, researchers divide subjects into groups (such as an experimental group and a control group) to manipulate variables and observe the effects. In an observational study, researchers only observe without dividing into groups for manipulation. In a survey, researchers collect data through questions rather than dividing subjects into groups for experimental manipulation.

Answer:

B. controlled experiment