Indicate whether each of the following descriptions better matches the rough (R) or the smooth (S) endoplasmic reticulum (ER). Your answer would be a five-letter string composed of letters R and S only, e.g. SRSRR.
( ) It mostly has a tubular appearance.
( ) It contains the transitional ER.
( ) It is coated by ribosomes.
( ) It can be specialized for functions such as detoxification and lipid metabolism.
( ) Sarcoplasmic reticulum in muscle cells is one of its specialized forms.