To determine which set of SI units contains only fundamental units, we need to understand what constitutes fundamental units in the International System of Units (SI). Fundamental units are the basic units from which all other units are derived. The fundamental SI units are:
1. Meter (m) - Unit of length
2. Kilogram (kg) - Unit of mass
3. Second (s) - Unit of time
4. Ampere (A) - Unit of electric current
5. Kelvin (K) - Unit of thermodynamic temperature
6. Mole (mol) - Unit of substance amount
7. Candela (cd) - Unit of luminous intensity
Now, let's analyze each set of units given in the question to identify which set consists solely of these fundamental units:
Option A:
- A (Ampere) - Fundamental unit
- mol (Mole) - Fundamental unit
- m² (Square meter) - Derived unit (derived from the fundamental unit of length, meter)
Option B:
- cd (Candela) - Fundamental unit
- mol (Mole) - Fundamental unit
- K (Kelvin) - Fundamental unit
Option C:
- N (Newton) - Derived unit (derived from kg·m/s²)
- cd (Candela) - Fundamental unit
- ms (Millisecond) - Derived unit (derived from the fundamental unit of time, second)
Option D:
- N (Newton) - Derived unit (derived from kg·m/s²)
- m (Meter) - Fundamental unit
- ms (Millisecond) - Derived unit (derived from the fundamental unit of time, second)
Option E:
- s (Second) - Fundamental unit
- J (Joule) - Derived unit (derived from kg·m²/s²)
- K (Kelvin) - Fundamental unit
Analyzing these options, we see that Option B (cd, mol, K) consists solely of fundamental SI units. Therefore, the correct answer is:
B. cd, mol, K
