Which nitrogenous base is present in $RNA$ but not in $DNA$?

The number of $H$-bonds between Guanine and Cytosine is .....

Assertion: In a $DNA$ molecule,$A-T$ rich parts melt before $G-C$ rich parts.
Reason: In between $A$ and $T$ there are three $H-$ bonds,whereas in between $G$ and $C$ there are two $H-$ bonds.

How many base pairs are present in each turn of the $DNA$ helix?

What is the number of phosphodiester bonds in a $DNA$ molecule containing $10$ base pairs?

What does $P$ represent in the given figure?