Si Units

As described in NCERT Class 11, Chapter 2 (Units and Measurements), the SI system is built upon seven base quantities, namely length, mass, time, electric current, thermodynamic temperature, amount of substance and luminous intensity, each with its own base unit. Luminous intensity, measured in candela, is one of these fundamental base quantities and cannot be expressed in terms of the others. Force is incorrect because it is a derived quantity expressed as mass times acceleration with the unit newton. Frequency is incorrect since it is derived from the inverse of time and measured in hertz. Energy is incorrect as it is derived from force and displacement, carrying the unit joule. A quick conceptual check confirms that base quantities are those chosen as independent foundations, while all three rejected options can be written using combinations of base units, proving they are derived.