Which of the following are not a unit of time ?

Options

A. second
B. Parsec
C. Year
D. Light year

Explanation

To determine which of the following options are not a unit of time, we will analyze each option provided:

1. **Option A: Second**
- The second is the SI (International System of Units) unit of time. It is universally recognized as a standard measure of time. Therefore, this is a unit of time.

2. **Option B: Parsec**
- A parsec is a unit of length used in astronomy to measure large distances, specifically the distance at which one astronomical unit subtends an angle of one arcsecond. Since it measures distance and not time, this is **not** a unit of time.

3. **Option C: Year**
- A year is a measure of time that represents the duration it takes for the Earth to complete one orbit around the Sun. It is commonly used in calendars and is a recognized unit of time. Therefore, this is a unit of time.

4. **Option D: Light Year**
- A light year is also a unit of distance, defined as the distance that light travels in one year. While it incorporates the concept of time (one year), it ultimately measures distance, not time. Thus, this is **not** a unit of time.

### Conclusion:
The options that are **not** units of time are:
- **B: Parsec**
- **D: Light Year**

### Step-by-Step Solution:
1. Identify the options provided: Second, Parsec, Year, Light Year.
2. Analyze each option to determine if it measures time.
3. Confirm that:
- Second is a unit of time.
- Parsec is a unit of length (not time).
- Year is a unit of time.
- Light Year is a unit of distance (not time).
4. Conclude that the options that are not units of time are Parsec and Light Year.