---- [Answer] ----
13. In horses, cows and other large plant eating animals, the appendix is large and used to help digest the food and to produce vitamins. In humans, the appendix is very small in size and has no apparent function.
In humans, we would say that the appendix is
a) a homologous organ.
b) an analogous organ.
c) a vestigial organ.
---- [Answer] ----