Cacti in the Deserts of Southwestern North America and Some

Cacti in the deserts of southwestern North America and some euphorbs of the deserts of Africa, have barrel-shaped stems, short-lived leaves, and spines, yet these two types of plants are from different evolutionary lineages. This is an example of

A) selective breeding.
B) transitional forms.
C) homologous traits.
D) convergent evolution.
E) concave evolution.