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 $30S$.

Many ribosomes may associate with a single $mRNA$ to form multiple copies of a polypeptide simultaneously. Such strings of ribosomes are termed as

Ribosomes are found in which of the following?

Granular structures found free in the cytoplasm as well as attached to the endoplasmic reticulum are:

Which of the following does not possess a lipid and protein-containing membrane?