Prokaryotic ribosomes have a diameter of ......... (in $, nm$)

Besides the nucleus,eukaryotic cells have other membrane-bound distinct structures called organelles. Which one is odd according to the given statement?

An element which helps in joining the subunits of ribosomes is

From the statements given below,choose the correct option:
$A.$ The eukaryotic ribosomes are $80S$ and prokaryotic ribosomes are $70S$.
$B.$ Each ribosome has two sub-units.
$C.$ The two sub-units of $80S$ ribosome are $60S$ and $40S$,while those of $70S$ are $50S$ and $30S$.
$D.$ The two sub-units of $80S$ ribosome are $60S$ and $20S$,and those of $70S$ are $50S$ and $20S$.
$E.$ The two sub-units of $80S$ ribosome are $60S$ and $30S$,and those of $70S$ are $50S$ and $30S$.

Peptide synthesis inside the cell occurs at:

$A$ polysome is formed by: