The correct option is D All of the above
Seed dormancy is defined as a condition in which seeds do not germinate even when the environmental conditions are favourable (i.e proper temperature, water, sunlight, air).
Seed dormancy may be caused because of the following reasons:
i) Impermeable and hard seed coat.
ii) Presence of chemical inhibitors like abscisic acid, phenolic acid, para-ascorbic acid.
iii) Immature embryos