The appendix in humans is a vestigial organ. In other mammals, it is not vestigial and is larger because it helps to digest a certain type of plant material. Which statement most likely describes the appendix’s lack of function in humans?

a-The diet of humans no longer includes as much plant material.
b-The diet of humans is the same as other mammals.
c- The human digestive system is less effective compared to other mammals. d-The human digestive system relies heavily on the appendix.