Question

the nucleus, ribosome, e.r., and mitochondria are all examples of in an animal cell. options: organ systems, cells, organelles, cytoplasm. (image shows labeled cell structures: nucleus, ribosome, centrosome, endoplasmic reticulum, mitochondrion, membrane)

Explanation:

The nucleus, ribosome, endoplasmic reticulum (E.R.), and mitochondria are structures within a cell that have specific functions. Organelles are specialized structures within a cell that perform distinct tasks. Organ systems are groups of organs, cells are the basic unit of life (and these are parts of cells, not the cells themselves), and cytoplasm is the fluid matrix in the cell (not the structures like nucleus etc.). So these are organelles.

Answer:

organelles