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

Pam was using steel to make rusted sculptures. After building each sculpture, she caused the steel in the sculpture to rust by placing it into a tub filled with salt water for eight hours. Pam wondered if steel would rust faster submerged in vinegar instead of salt water.
To find out, Pam cut ten squares of steel sheet metal and split them into two equal groups. She put one group of squares into a tub filled with salt water and the other group of squares into a tub filled with vinegar. Once an hour for eight hours, Pam counted the number of rusted steel squares in each group.
Hint: An independent variable is a variable whose effect you are investigating. A dependent variable is a variable that you measure.
Figure: a sculpture made from rusted steel.
Which of the following was a dependent variable in this experiment?
A. the type of liquid used
B. the number of rusted steel squares
From the given choices, select the correct answer and reply with the letter of the chosen option.

B