Which of the following is not a unit of time
A) par sec B) light year C) micron D) sec

Options

A. Only A
B. A and B
C. A, B & C
D. A, B , C , D

Answer

To solve the question "Which of the following is not a unit of time?" we need to analyze each option provided.

### Step 1: Analyze Option A - Parsec
- A parsec is a unit of distance used in astronomy. It is defined as the distance at which one astronomical unit subtends an angle of one arcsecond. Therefore, parsec is not a unit of time.

### Step 2: Analyze Option B - Light Year
- A light year is also a unit of distance. It is defined as the distance that light travels in one year. Since it measures distance, it is not a unit of time.

### Step 3: Analyze Option C - Micron
- A micron (or micrometer) is equal to \(10^{-6}\) meters. It is a unit of length, not time. Therefore, micron is also not a unit of time.

### Step 4: Analyze Option D - Seconds
- Seconds are the standard unit of time in the International System of Units (SI). It is the base unit for measuring time, where 60 seconds make one minute. Thus, seconds are indeed a unit of time.

### Conclusion
From the analysis:
- Options A (parsec), B (light year), and C (micron) are not units of time.
- Option D (seconds) is a unit of time.

Therefore, the correct answer is **A, B, and C** are not units of time.

### Final Answer
The answer is: **A, B, and C**.

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