A new physical therapy is being tested in an experimental setting to see if the new methods reduce the recovery time for patients who recently
underwent surgery for a torn ACL, a ligament in your knee. To do this, the
researchers in the study first performed intake on participants by observing
their Body Mass Index (BMI) and had them take a survey to describe their
diet and their exercise habits.
Then, the participants were split into three groups: the first group received
no physical therapy, the second group received traditional physical therapy,
and the third group received the new experimental physical therapy.
The group which receives no physical therapy would best be described as
which of the following?

Explanatory Variable
Response Group
Experimental Unit
Control Group