Concept:Double fertilisation is a reproductive mechanism unique to flowering plants, known as angiosperms.
Explanation:In angiosperms, the female gametophyte, called the embryo sac, contains an egg cell and two polar nuclei.
When pollen reaches the ovule, a pollen tube delivers two male gametes, or sperm cells, into the embryo sac.
One male gamete fuses with the egg cell to form the zygote, which develops into the embryo.
The second male gamete fuses with the two polar nuclei in a process called triple fusion, producing the endosperm nucleus.
This endosperm nourishes the developing embryo.
Because both fertilisation events occur together within the embryo sac, the overall process is known as double fertilisation.
Bryophytes, pteridophytes, and algae do not perform this dual fusion.
Therefore, double fertilisation is a distinctive feature of angiosperms only.
Answer:A. Angiosperms