Context: The passage below describes an experiment. Read the passage and think about the variables that are described.

Lindsey had four air plants on her desk that were not growing. She suspected that they needed more water. Lindsey's sister recommended soaking the air plants in a bowl of water once a week. Lindsey's coworker recommended spraying the air plants with a mist of water every day.
Lindsey decided to test both ideas. First, she measured the initial weight of all four air plants. Then, for the next two months, she sprayed two of the plants with a mist of water each day. She watered the two remaining plants by soaking them in water once a week. Finally, Lindsey measured the weight of the plants again and calculated the change in weight for each plant.
Hint: An independent variable is a variable whose effect you are investigating. A dependent variable is a variable that you measure.
Figure: an air plant displayed on a rock.
Which of the following was an independent variable in this experiment?
A. the change in weight for each plant
B. the watering method used
Answer with the option's letter from the given choices directly.

B