Biology

The correct answer is: A. Yeast.

1. Understand the principle of determining close - relatedness in a phylogenetic tree:

In a phylogenetic tree, the closer two organisms are in terms of the most recent common ancestor they share, the more closely related they are. The fewer the number of branching points between two organisms, the more recent their common ancestor.

2. Analyze each option:

Yeast: The branch of yeast and the branch of humans diverge from a common ancestor with relatively few other organisms in between on their respective branches. Compared to the other options, the common ancestor of yeast and humans is more recent.