Answer:
a. They contain nutritive tissue for the embryo.
b. They contain an embryo.
Explanation:
Seeds are formed from fertilized ovules which consist of small embryo surrounded by the protective seed coat. The endosperm of the seed stores food for the nutrition of the embryo.
Seed results from double fertilization process in angiosperms. The egg fuses with the sperm nuclei to produce the zygote while the polar nuclei which is essentially a diploid structure fuses with another haploid sperm cell to form the triploid endosperm.
The endosperm surrounds the embryo and stores foods for the development of the embryo.