Enzymes are synthesized on the ........

Which of the following is an organelle present within another organelle?

An element which helps in joining the subunits of ribosomes is

$80S$ ribosomes $= .............$

What is attached to the outer surface of the endoplasmic reticulum in actively synthesizing cells?

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 $30S$.