The endoplasmic reticulum is present in:-

Options

A. Nucleus
B. Chromosomes
C. Nucleolus
D. Cytoplasm

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks where the endoplasmic reticulum (ER) is present. We need to analyze the given options to determine the correct answer.

2. **Analyzing the Options**:
- **Option 1: Nucleus**: The nucleus is a membrane-bound organelle that contains the cell's genetic material. While the endoplasmic reticulum is connected to the nuclear membrane, it is not located within the nucleus itself. Therefore, this option is incorrect.

- **Option 2: Chromosome**: Chromosomes are structures within the nucleus that carry genetic information. They are not organelles and do not contain the endoplasmic reticulum. Thus, this option is also incorrect.

- **Option 3: Nucleolus**: The nucleolus is a dense region within the nucleus where ribosome synthesis occurs. It is not a location where the endoplasmic reticulum is found. Hence, this option is incorrect as well.

- **Option 4: Cytoplasm**: The endoplasmic reticulum is located in the cytoplasm of eukaryotic cells. It is a network of membranes that plays a crucial role in protein and lipid synthesis. This option is correct.

3. **Conclusion**: The endoplasmic reticulum is present in the cytoplasm of eukaryotic cells. Therefore, the correct answer is **Option 4: Cytoplasm**.