The Mass Extinction at the End of the Ordovician Period

The mass extinction at the end of the Ordovician period killed

A) 50 percent of marine animal families, including many trilobites.
B) 50 percent of terrestrial and marine animal families, including many trilobites.
C) 90 percent of terrestrial and marine animal families, and 100 percent of terrestrial plants.
D) 100 percent of trilobites and 90 percent of terrestrial and marine animal families.