Variables are physical, chemical or biological quantities of characteristics.

• A. Data sets.
• B. Variables.
• C. Units.
• D. Controls.

Answer: (B)

The idea is that a variable is something you can measure that can take different values, describing a characteristic of the system being studied. These measurable properties can be physical (like length or temperature), chemical (like pH or concentration), or biological (like heart rate or enzyme activity). Because a variable is about the quantity you observe that can change, it fits the description given. Data sets are just collections of measurements, units are the standards used to measure (like meters or seconds), and controls are parts of the experiment kept the same to ensure fair comparison. So the statement points to the concept of quantities that describe characteristics and can vary.