Endospermic seeds are found in which of the following plants?

The correct answer is Option (4) → All of these

Endosperm is the food-storing tissue of the seed. In some seeds the developing embryo uses it up completely (pea, groundnut, beans); these are non-albuminous seeds. In others a part of the endosperm stays in the mature seed and is used during germination. These are albuminous or endospermic seeds.

Option (1) Castor — Correct statement, but it is only one of the correct points, so on its own it is not the answer. Castor is an albuminous seed. Its endosperm persists in the mature seed.

Option (2) Barley — Correct statement, but it is only one of the correct points, so on its own it is not the answer. Barley, like the other cereals wheat and maize, keeps a part of its endosperm, so it is an albuminous seed.

Option (3) Coconut — Correct statement, but it is only one of the correct points, so on its own it is not the answer. In coconut the endosperm persists. The coconut water is the free-nuclear endosperm and the white kernel around it is the cellular endosperm.

NCERT Extract:
Seed – “… Mature seeds may be non-albuminous or ex-albuminous. Nonalbuminous seeds have no residual endosperm as it is completely consumed during embryo development (e.g., pea, groundnut). Albuminous seeds retain a part of endosperm as it is not completely used up during embryo development (e.g., wheat, maize, barley, castor).”
Endosperm – “… Endosperm may either be completely consumed by the developing embryo (e.g., pea, groundnut, beans) before seed maturation or it may persist in the mature seed (e.g. castor and coconut) and be used up during seed germination.”