Which of these trees is different from the rest? Hint, don't panic by seeing the diagrams, this is straightforward: Look at them for what they are and address the question:
None, they are all the same.
After the K-T extinction, mammals filled many niches that had previously been filled with the newly extinct species. Now, mammals are prolific in most continents. This process is called:
A speciation event
An adaptive radiation
The Cambrian explosion
Competitive exclusion
The mammalian explosion