Which of these things is not part of the nucleus of cell?

Options

A. Endoplasmic reticulum
B. Chromosomes
C. Nucleolus
D. nucleoplasm

Explanation

To determine which of the given options is not part of the nucleus of a cell, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understand the Components of the Nucleus**:
- The nucleus is a double membrane-bound organelle found in eukaryotic cells. It contains genetic material (DNA) and is involved in various cellular processes.

2. **Evaluate the Options**:
- **Option 1: Endoplasmic Reticulum (ER)**:
- The endoplasmic reticulum is an organelle that is associated with the nucleus but is not part of it. It exists outside the nucleus and plays a role in protein and lipid synthesis.
- **Option 2: Chromosome**:
- Chromosomes are structures made of DNA and proteins that are located within the nucleus. They carry genetic information and are definitely part of the nucleus.
- **Option 3: Nucleus**:
- This option refers to the nucleus itself, which is obviously part of the nucleus.
- **Option 4: Nucleoplasm**:
- Nucleoplasm is the gel-like substance within the nucleus that contains the chromatin and nucleolus. It is indeed part of the nucleus.

3. **Identify the Correct Answer**:
- Based on the analysis, the only option that is not part of the nucleus is the **Endoplasmic Reticulum**.

### Final Answer:
The correct answer is **Endoplasmic Reticulum**.