Identify the correct statement with respect to ribosomes.

The correct option is B Mg${}^{++}$ concentration affects the binding of two subunits.
Ribosomes are submicroscopic polypeptide manufacturing naked granular nucleoprotein organelles which were first seen by Claude in 1941. Cytoplasmic ribosomes of eukaryotes are of 80S type (made up of two subunits of 60S and 40 S type) while their organellar and prokaryotic ribosomes are of 70 S type (made up of two subunits of 50S and 30S type). Magnesium ion is essential for binding the ribosome subunits. The value is 1 to 2 mM for eukaryotes and 0.5 mM in prokaryotes. The subunits separate below this concentration. Disintegration occurs at a magnesium ion level 0.5 mM in eukaryotes and below 0.3 mM in prokaryotes. The ribosomes form dimers when magnesium ion concentration is high.