13. On a per unit basis, which of the following would be the most expensive to build energetically? (A) A moss plant that is entirely parenchyma. (B) A herbaceous plant that consists mainly of parenchyma, collenchyma, and vascular tissue. (C) A cactus that consists mainly of parenchyma but also contains vascular tissue and sclerenchymatous spines. (D) A woody plant composed mainly of xylem, plus some parenchyma and phloem. (E) An aquatic plant that contains mainly aerenchyma, in addition to vascular tissue.