Context: The passage below describes an experiment.

Craig worked in a restaurant that had a vegetable garden. Part of his job was to care for the tomato plants. He had heard that pruning, or trimming, tomato plants can help tomatoes grow. He wondered if pruning would affect how well his tomato plants grew.
Craig chose 24 tomato plants that were similar in size. He pruned an equal number of branches from each of the first 12 plants. He left the other 12 plants unpruned. Then, each week, Craig weighed the tomatoes that he picked from each group of plants.
Figure: a tomato plant.
In this experiment, which were part of a control group?
A. the unpruned tomato plants
B. the pruned tomato plants
From the given choices, pick the correct answer and respond by indicating the letter of the correct option.

A