What is double fertilization in Angiosperms

Number of nuclei taking part in double fertilization is

What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.

In angiospermic fertilisation, one male gamete fuses with egg to form ...$A$... , this event is called ...$B$....

Identify $A$ and $B$ and choose the correct option

What is meant by double fertilization? Explain.

By double fertilization is formed