This answer is unsupported. Rodents have chisel-like incisors, but most North American mammal species are not rodents. And we don't know if any other mammal species have chisel-like incisors.

This answer is strongly supported. In North America, most mammal species are not rodents, and yet most individual mammals in North America are rodents. The only way this is possible is if rodent species typically have more members.

This answer is unsupported. The stimulus only discusses North American species, so it's impossible for us to make a comparison between species in North America and elsewhere in the world.

This answer is unsupported. We can only infer from the stimulus that rodent species in general have more members. There could still be a single non-rodent species with more members than any rodent species.

This answer is unsupported. Like in (C), we don’t have any information from the stimulus about species outside of North America to make this comparison.