Answer:
Group B
Step-by-step explanation:
A Control group is standard that allows for comparisons to be made in an experiment.
Control groups helps to ensure accuracy and many experiment includes a control group.
Control is often time identical with the experimental group but experimental group is often subjected to treatment while the control group are not as the treatment this is to identify the changes due to the treatment. Therefore, Group A that was given verbal praise is the experimental group and the praise is the treatment while group B without praise is the control.