In $r-RNA$, the '$r$' stands for .......

Which one of the following structures is an organelle within an organelle?

Which type of ribosomes are found in prokaryotes (in $S$)?

Protein synthesis in an animal cell occurs

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 $30S$.

What are the two subunits of $80S$ ribosomes?