A plant leaf is a photosynthetic organ of the plant which contains the chlorophyll pigment. The plants have the ability to form new leaves or young leaves when the older leaves shed away.
The younger and older plant leaves can be distinguished on the basis of their color.
The younger leaves as they grow to appear darker due to the presence of higher number of chlorophyll pigments which imparts green color. But as the leaves got older, the color of the leaves changes to yellow as they necrosis leads to the death of the leaves and the anthocyanin pigment imparts yellow color.
This is because in DNA, purines (A and G), pair with pyrimidines (C and T), and more specifically, adenine pairs with thymine and cytosine pairs with guanine. Per this base pairing, B should be the right answer.
