Question

what is the main function of the endoplasmic reticulum in an animal cell?
to help ribosomes make proteins
to break down waste and worn - out cell parts
to fill the space between the cell membrane and the nucleus
to direct cell activities by sending instructions to different
parts of the cell

Explanation:

The endoplasmic reticulum (ER) in an animal cell, especially the rough ER (with ribosomes), helps ribosomes in protein synthesis. The other options: filling space is cytoplasm, breaking down waste is lysosomes, directing activities is the nucleus. So the main function related to ER and ribosomes is helping make proteins.

Answer:

to help ribosomes make proteins