If endoplasmic reticulum are membranes attached to sites where proteins are made, then what are membranes attached to sites where proteins are made?

Answer choices:
- the body's largest organ
 - Veins and arteries.
 - epidermis and dermis
 - layers of fat
 - cell walls
 - cell membranes
 - endoplasmic reticulum
 - brain cells

 

       endoplasmic reticulum   