The double-helical structure of $DNA$ is due to the action of . . . . . . .

The $AT/GC$ ratio in human beings is (where $A = \text{adenine}$,$T = \text{thymine}$,$G = \text{guanine}$,$C = \text{cytosine}$)

Identify the set containing purine and pyrimidine base of $DNA$ respectively.

What type of sugar molecule is present in $DNA$?

Which among the following is a double ring containing nitrogen base present in nucleic acids?

Given below are two statements:
Statement $I$: Cytosine and guanine are formed in equal quantities in $DNA$ hydrolysis.
Statement $II$: Adenine and uracil are formed in equal quantities in $RNA$ hydrolysis.
The correct answer is: