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

Michelle was learning to bake bread at home. Her first few batches of dough did not rise, or expand, as much as they should have. Michelle's mother noted that the kitchen was cold and suggested that the dough might not be warm enough to rise.
Michelle decided to test her mother's suggestion. She made a large batch of dough and divided it into six equal-sized balls. Then, she put each ball into a bowl. She left three bowls on the counter in the kitchen, where the temperature was 63°F. She left the other three bowls on her desk in her upstairs bedroom, where the temperature was 80°F. After one hour, Michelle measured the size of each dough ball.
Hint: An independent variable is a variable whose effect you are investigating. A dependent variable is a variable that you measure.
Figure: bread dough left in a bowl to rise.
Which of the following was an independent variable in this experiment?
A. the size of each dough ball
B. the temperature where the dough was left to rise
From the given choices, select the correct answer and reply with the letter of the chosen option.

B