Which of the following cannot be used for measurement of time?

Options

A. A leaking tap.
B. Simple pendulum.
C. Shadow of an object during the day.
D. Blinking of eyes.

Explanation

To determine which of the following cannot be used for the measurement of time, we need to analyze the options given.

1. **Understanding Time Measurement**: Time can be measured using various methods and tools that provide a consistent and periodic interval. Examples include clocks, sundials, and other devices that have a regular cycle.

2. **Analyzing the Options**:
- **Option 1**: Shadow of an object during the day (e.g., sundial) - This can be used to measure time as the position of the shadow changes with the sun's movement.
- **Option 2**: Clocks - These are standard instruments for measuring time.
- **Option 3**: Hourglass - This also measures time through the flow of sand, which occurs at a consistent rate.
- **Option 4**: Blinking of eyes - This does not have a fixed interval; it is irregular and varies from person to person.

3. **Conclusion**: Among the options, the blinking of eyes cannot be used for the measurement of time because it does not occur at regular intervals. Therefore, the correct answer is **Option 4: Blinking of eyes**.

### Step-by-Step Solution:
1. Identify the purpose of the question: To find out which option cannot be used for measuring time.
2. Review each option to see if it provides a consistent and periodic measurement.
3. Determine that the shadow of an object, clocks, and hourglasses can all measure time.
4. Conclude that the blinking of eyes is irregular and does not provide a reliable measurement of time.
5. State the final answer: Blinking of eyes cannot be used for measurement of time.