The correct option is **C. Force**. ### Detailed Explanation In the International System of Units (SI), quantities are classified into two main categories: **base quantities** and **derived quantities**. 1. **Base Quantities**: These are the fundamental physical quantities from which other quantities can be derived. The seven base quantities in the SI system are: - **Mass** (kilogram, kg) - **Length** (meter, m) - **Time** (second, s) - **Electric current** (ampere, A) - **Thermodynamic temperature** (kelvin, K) - **Amount of substance** (mole, mol) - **Luminous intensity** (candela, cd) 2. **Derived Quantities**: These are quantities that are derived from the base quantities through mathematical relationships. They are expressed in terms of the base quantities. For example: - **Force** is a derived quantity defined by Newton's second law of motion, which states that force equals mass times acceleration (F = ma). Here, force is measured in newtons (N), where 1 N = 1 kg·m/s². Thus, force is derived from the base quantities of mass (kg) and length (m) and time (s). ### Why the Other Options Are Incorrect - **A. Mass**: This is a base quantity in the SI system. It is one of the fundamental measurements and is not derived from any other quantities. - **B. Length**: Like mass, length is also a base quantity. It is measured in meters (m) and serves as a fundamental measurement in physics. - **D. Time**: Time is another base quantity in the SI system, measured in seconds (s). It is essential for measuring the duration of events and is not derived from other quantities. ### Summary of Key Points - **Force** is a derived quantity because it is calculated from the base quantities of mass and acceleration. - **Mass**, **Length**, and **Time** are all base quantities in the SI system and are not derived from other measurements. - Understanding the distinction between base and derived quantities is crucial for solving problems in physics and applying the correct units. ### Revision Summary - **Base quantities** include mass, length, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity. - **Derived quantities** are formed from base quantities, such as force (F = ma). - **Force** is measured in newtons (N), which is derived from kg·m/s². - Recognizing the difference between base and derived quantities is essential for mastering physics concepts.