Assertion : The nitrogen bases of the two chains of DNA are held together by hydrogen bonds.
Reason : Both chains of DNA are anitparallel.

Options

A. If both the assertion and the reason are true and the reason is a correct explanation of the assertion
B. If both the assertion and reason are true but the reason is not a correct explanation of the assertion
C. If the assertion is true but the reason is false
D. If both the assertion and reason are false

Answer

B

Explanation

Both chains of DNA are antiparallel i.e. one strand in 5.-3. direction.
DNA is polymer made up of nitrogenous bases that are held together by hydrogen bond i.e. A = T (Adenine bonded by Thymine with double hydrogen bond) and CG ≡ (Guanine with cytosine by these hydrogen bond).