Cladistics is a classification system based on a. nomenclature
b. dichotomous keys
c. common ancestry
d. physical characteristics

c

Explanation:

cladistics is based on evolutionary ancestry and generates trees called cladograms. Cladistics also identifies clades, which are groups of organisms that include an ancestor species and its descendants. Classifying organisms on the basis of descent from a common ancestor is called phylogenetic classification.

it's unlikely a majority of a large population would agree on issues

hope this : )

i am going to guess that it is co2.