In the S.I. units the number of basic physical quantities is

Options

A. 3
B. 7
C. 9
D. 21

Answer

To solve the question regarding the number of basic physical quantities in the S.I. units, we will follow these steps:

### Step 1: Identify Basic Physical Quantities
We need to list the basic physical quantities defined in the International System of Units (S.I. units).

### Step 2: List the Basic Physical Quantities
1. **Length** - The unit is meter (m).
2. **Mass** - The unit is kilogram (kg).
3. **Time** - The unit is second (s).
4. **Electric Current** - The unit is ampere (A).
5. **Temperature** - The unit is kelvin (K).
6. **Amount of Substance** - The unit is mole (mol).
7. **Luminous Intensity** - The unit is candela (cd).

### Step 3: Count the Basic Physical Quantities
Now, we count the quantities listed above:
- Length
- Mass
- Time
- Electric Current
- Temperature
- Amount of Substance
- Luminous Intensity

### Step 4: Conclusion
We find that there are a total of **seven** basic physical quantities in the S.I. units.

### Final Answer
The number of basic physical quantities in the S.I. units is **7**.

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