What are polynucleotides made of?

If the sequence of one strand of $DNA$ is written as follows:
$5'- ATGCATGCATGCATGCATGCATGCATGC-3'$
Write down the sequence of the complementary strand in the $5' \rightarrow 3'$ direction.

The molecular effect of ultraviolet light is primarily mediated by:

In what way does $DNA$ differ from $RNA$?

Find the correct palindromic sequence for the given $DNA$ strand:
$5'ATTGCAAT3'$

Chargaff's rules are applicable to