Which of the following statements describe double fertilisation in flowering plants?

The correct option is B Fusion of the egg cell with one male gamete and fusion of polar nuclei with one male gamete.
Double fertilisation is unique to flowering plants. It is called double fertilisation because there are two types of fusion that occur within the embryo sac (syngamy and triple fusion).

In flowering plants, two male gametes are formed inside each pollen grain. These are carried to the embryo sac through pollen tube.

One haploid male gamete fuses with the haploid female gamete (egg cell) to form the diploid zygote. This fusion is called syngamy.

Another male gamete fuses with the two polar nuclei to form the primary endosperm nucleus (PEN). This is called triple fusion.

As there are two types of fusion, one is syngamy and another one is triple fusion, this phenomenon is termed as double fertilisation.