Final answer:
On a phylogenetic tree, C. the horizontal axis represents time, with evolutionary events depicted in order from the common ancestor towards present. Branch lengths do not necessarily indicate time duration unless specified.
Step-by-step explanation:
If a phylogenetic tree depicts extant taxa on the right and the point of most recent common ancestry on the left, then the correct statement is that the horizontal axis represents time. This means that as one moves horizontally from left to right, they are moving forward in time from the most recent common ancestor towards the present. The horizontal representation in a phylogenetic tree shows the chronological order of evolutionary events, but unless otherwise indicated, the branches of the tree do not signify the length of time. It is important to note that long branches on the tree do not necessarily correspond to more time having passed and vice versa, unless this is explicitly stated on the diagram.
A rooted phylogenetic tree begins with a common ancestor from which all organisms in the tree are descended. The branching points on a phylogenetic tree, called branch points, indicate where a single lineage evolved into distinct new ones. The concept that shared characteristics are used to construct these phylogenetic trees helps in understanding how closely related different species are based on their common ancestry.