Final answer:
The correct answer to the student's question is c, stating that the event at the end of the Triassic resulted in the extinction of fewer faunas than other major extinction events, though it is critical to acknowledge that the end-Permian extinction was the largest in history.
Step-by-step explanation:
The student asked which statement is correct about the changes in faunas during one of the five major extinction events. Considering the provided information, the correct answer is that the mass extinction event at the end of the Cretaceous period, which is known as the Cretaceous-Paleogene (K-Pg) mass extinction, led to significant changes in the world's faunas. Specifically, the K-Pg extinction event resulted in the extinction of dinosaurs and many other species, greatly reducing biodiversity and leading to fewer shapes of pollen grains seen in the fossil record, indicative of a loss of plant diversity. After this event, ferns became more abundant, filling in the ecological niches left vacant by the extinct species.
Additionally, the Permian extinction event, which occurred at the end of the Permian period, is recognized as the most catastrophic mass extinction event in Earth's history with an estimated 95 percent of species lost. The Devonian extinction had a considerable impact on marine species, but the effect on terrestrial species was less prominent. Contrary to statement a, the event at the end of the Devonian did not result in an increase in Cambrian faunas, and b is incorrect as well because the Cretaceous event did not increase the number of Paleozoic faunas.
Lastly, regarding statement c, the end of the Triassic did lead to significant extinctions but was not the period with the fewest extinctions. Statement d incorrectly suggests that the end of the Cretaceous resulted in the extinction of more faunas than any other period, which is untrue as the end-Permian extinction was larger. Thus, the information provided suggests that the statement about the Triassic period is the most accurate when considering the relative scale of these extinction events.