The Gymnosperm Gnetophytes Are Known to Have Diversified Alongside Early

The gymnosperm gnetophytes are known to have diversified alongside early angiosperms in Cretaceous tropical forests. The presence of what general features may account for the fact that tropical forests are dominated (in terms of both ecological importance and diversity) by eudicots and monocots and not gnetophytes today?

A) xylem with vessels
B) tightly coevolved reproductive structures and animal pollinators
C) reduced apical dominance
D) double fertilization
E) herbaceous growth forms