​Match the following ribose sugar pucker in nucleic acids (labeled A, B, C, D) with their corresponding conformational states. The black circle denotes the base of the nucleotide.​

Correct option is B

EXPLANATION-

In ribose puckers, atoms can be classified as endo (above the ring plane) or exo (below the ring plane).

Structure A - C2′ is above the plane of the ribose ring.
This is a C2′-endo conformation.

Structure B - O4′ is above the plane of the ribose ring.
This is a O4′-endo conformation.
​
Structure C - C3′ is above the plane.
This is a C3′-endo conformation.

Structure D - O4′ is below the plane, hence exo.
This is a O4′-exo conformation.

So, the correct option is (b) - A – C2’–endo; B – O4’–endo; C – C3’–endo; D – O4’–exo