Which of the following organelles contain ribosomes?

What is meant by the Endomembrane system? Which cell organelles are included in it? Provide brief information.

Which of the following statements is/are correct?
$(i)$ The endomembrane system includes plasma membrane,$ER$,Golgi complex,lysosomes and vacuoles.
$(ii)$ $ER$ helps in the transport of substances,synthesis of proteins,lipoproteins and glycogen.
$(iii)$ Ribosomes are involved in protein synthesis.
$(iv)$ Mitochondria help in oxidative phosphorylation and generation of $ATP$.

In the given figure,what do the labeled parts '$a$' and '$b$' represent respectively?

The cell is considered one of the wonders of the world because...

The magnifying power of the oil immersion lens in a light compound microscope is . . . . . . . (in $X$)