Which among the following is incorrect about endoplasmic reticulum?

• A. These are complex network of membrane bounded tubules
• B. They are classified as smooth and rough endoplasmic reticulum
• C. Smooth endoplasmic reticulum has ribosomes attached to their surface and acts as site of protein synthesis
• D. Rough endoplasmic reticulum is connected by nuclear membrane at one end and golgi apparatus on the other end