Statement A: In prokaryotic cell, ribosomes are associated with plasma membrane.Statement B: The sub-units of of prokaryotic ribosomes are 50S and 20S that together form 70S ribosomes.

The 70S ribosomes of prokaryotes with subunits as 50S and 30S occur either freely in the cytoplasm or attached to inner surface of cell membrane. The ribosomes may be attached to common mRNA to form polysome or polyribosome or ergosome.