Which Polyploidization Mechanism Is Thought to Occur Most Often in Plants

Which polyploidization mechanism is thought to occur most often in plants?

A) Two related species mate, forming an organism with the combined chromosomes from both parents.
B) A single-celled embryo duplicates its chromosomes, but they are not separated into separate cells and remain in a single cell that develops into a viable embryo.
C) Chromosomes spontaneously split down the middle during the G1 portion of the cell cycle.
D) Plants form a syncytium.
E) There is a spontaneous duplication of chromosomes at random.