With which nitrogenous base does cytosine pair?

Which of the following is correct for Watson and Crick's model of $DNA$? It is a duplex with

Distinguish between: Repetitive $DNA$ and Satellite $DNA$.

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.

If a double stranded $DNA$ has $20\; \%$ of cytosine,what will be the percentage of adenine in it (in $; \%$)?

How many nucleotides are present in one turn of $DNA$ helix (in $pairs$)?