Final answer:
Among the options provided, the length of a person's arm is a variable because it can vary between individuals and change over time.
Step-by-step explanation:
The question you've asked is about identifying a variable among a list of quantities. A variable is a quantity that can change or vary, while a constant remains the same. Looking at the options provided:
- A. Number of minutes in an hour is a constant, because there are always 60 minutes in an hour.
- B. Number of inches in a foot is a constant, as there are always 12 inches in one foot.
- C. Length of a person's arm is a variable because the length can vary from person to person, and even for a single person over time.
- D. Length of the Brooklyn Bridge is generally considered a constant since it doesn't change significantly.
Therefore, the correct answer is C. Length of a person's arm.