A) Double fertilisation is unique to gymnosperms and monocotyledons
B) Sequoia, a gymnosperm, is one of the tallest trees
C) Phaeophyceae members possess chlorophyll-a, c, carotenoids and xanthophylls
D) Moss is a gametophyte, which consists of two stages namely, protonema stage and leafy stage
Explanation
True fertilisation together with triple fusion is known as double fertilisation, a unique phenomenon only occurs in angiosperms (absent in gymnosperms with few exception) and first time demonstrated by Nawaschin in Fritillaria and Lilium