$A$ polysome is a chain of .......

Polyribosomes are aggregations of:

The site for protein synthesis in plants is.......

The size of ribosomes is $.......$

Which cell organelle is described by the following statements?
$(A)$ Granular structure.
$(B)$ First observed under an electron microscope as dense particles by $George\, Palade$.
$(C)$ Composed of $RNA$ and proteins.
$(D)$ Not surrounded by any membrane.

What are the two subunits of $70S$ ribosomes?