Context: The passage below describes an experiment.

Martina had six air plants on her desk that were not growing. Once a week, she soaked the air plants in water. But she suspected that they needed more water. She wondered if spraying the air plants with water every day in addition to soaking them would help them grow.
Martina measured the initial weight of all six air plants. Then, for the next month, she continued to soak all of the air plants once a week. She also sprayed three of the plants every day. At the end of the month, Martina measured the weights of the plants again.
Figure: an air plant displayed on a rock.
In this experiment, which were part of an experimental group?
A. the plants that were soaked in water and sprayed
B. the plants that were only soaked in water
From the given choices, pick the correct answer and respond by indicating the letter of the correct option.
Answer: A