How does ER arise ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Endoplasmic Reticulum (ER):** The endoplasmic reticulum (ER) is a complex network of membranes found within eukaryotic cells. It plays a crucial role in the synthesis of proteins and lipids.

2. **Origin of ER:** The endoplasmic reticulum arises from the nuclear envelope, which is the double membrane surrounding the nucleus of a cell.

3. **Nuclear Envelope Structure:** The nuclear envelope consists of an inner and an outer membrane. The outer membrane is continuous with the endoplasmic reticulum.

...