Context: The passage below describes an experiment.

Vincent's young son drew all over the living room wall with crayons! Vincent wanted to find a way to remove the crayon markings. Based on what he read online, he decided to see if scrubbing a wall with baking soda could help remove crayon.
Vincent dipped a sponge in water and used it to scrub the crayon on a small section of the wall. He dipped a second sponge in water, sprinkled it with baking soda, and used it to scrub the crayon on another section of the wall. He observed how much crayon was removed from each section. Vincent repeated this test two more times on other sections of the wall.
Figure: scrubbing a crayon drawing off a wall.
In this experiment, which were part of an experimental group?
A. the sections of wall scrubbed with water only
B. the sections of wall scrubbed with water and baking soda
Select the correct answer from the given choices and respond with the letter of the chosen option.

B