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

Every day at work, Valentina poured a large cup of tea that she drank throughout the morning. She wondered how much bacteria might be growing in her cup of tea as the morning went on.
To find out, Valentina filled three identical cups with tea and placed them on her desk for three hours. After the first hour, she placed a drop of the tea from each cup on a separate microscope slide and counted the number of bacteria in the drop. Valentina repeated this with each cup of tea after the second hour, and again after the third hour.
Hint: An independent variable is a variable whose effect you are investigating. A dependent variable is a variable that you measure.
Figure: using a microscope to count bacteria on a slide.
Which of the following was a dependent variable in this experiment?
A. the number of bacteria in a drop of tea
B. the amount of time that the tea sat on the desk
Identify the correct choice from the options below and respond with the letter of the correct option.
Answer: A