The power of a lens can't be measured in

Options

A. m
B. W
C. h.p.
D. all the above

Explanation

To solve the question "The power of a lens can't be measured in," we need to analyze the options provided and determine which units are not applicable for measuring the power of a lens.

### Step-by-Step Solution:

1. **Understanding Power of a Lens**:
- The power of a lens is defined as the ability of the lens to converge or diverge light. It is measured in diopters (D).

2. **Identifying the Units**:
- The question lists several units: meter, watt, and horsepower. We need to evaluate each one to see if it can be used to measure the power of a lens.

3. **Analyzing the First Option - Meter**:
- Meter (m) is a unit of length. Since power is not a measure of length, we cannot use meters to measure the power of a lens.

4. **Analyzing the Second Option - Watt**:
- Watt (W) is a unit of power in the context of energy. It is defined as joules per second (J/s). Since the power of a lens is not related to energy in this way, we cannot use watts to measure the power of a lens.

5. **Analyzing the Third Option - Horsepower**:
- Horsepower (HP) is another unit of power, equivalent to 746 watts. Like watts, it is also not applicable for measuring the power of a lens.

6. **Conclusion**:
- Since none of the units (meter, watt, horsepower) can be used to measure the power of a lens, the correct answer is that the power of a lens cannot be measured in any of these units.

### Final Answer:
The power of a lens can't be measured in meter, watt, or horsepower.