Arrange the following events that occur in the embryo sac of angiosperms in a sequence at the time and after double fertilization. 
A. Syngamy  
B. Embryo development  
C. Triple fusion  
D. Endosperm formation

During double fertilization there is first syngamy or zygotic fertilization and later triple fusion or vegetative fertilization takes place. Since nutrients are required for the development of embryo from zygote, initially there is formation of some endosperm and later embryogeny is triggered.