Which of the following is without exception in Angiosperms : -

Double fertilisation (one male gamete fuses with the egg and the other with the polar nuclei) occurs in all angiosperms; it is a unique and universal feature of this group.
Vessels are absent in some primitive angiosperms (e.g. Wintera, Trochodendron).
Secondary growth is absent in most monocots.
Some angiosperms are not autotrophic, e.g. the parasite Cuscuta and saprophyte Monotropa.
So double fertilisation is without exception in angiosperms.