Question

what is the main function of the rough endoplasmic reticulum in an animal cell? to store water, waste, and nutrients, such as sugar, in the cell to break down waste and worn - out cell parts to help ribosomes make proteins to support movement within the cell

Explanation:

The rough endoplasmic reticulum (RER) has ribosomes attached to its surface. Ribosomes are involved in protein synthesis. The RER helps in the proper folding and initial modification of these newly - synthesized proteins.
Storing water, waste, and nutrients is mainly the function of vacuoles (in plant cells, large central vacuole; in animal cells, small vacuoles). Breaking down waste and worn - out cell parts is the function of lysosomes. Supporting movement within the cell is more related to the cytoskeleton (microfilaments, microtubules etc.).

Answer:

to help ribosomes make proteins