In mathematics, equivalence classes are a very important concept.

Polychaete worms play an important role in the seabed ecosystem.

The government declared a state of emergency to prevent the spread of the new coronavirus.

Cephalopods are a type of marine life that includes squid and octopus.

He is always hanging out with bad friends. Truly, birds of a feather flock together.

He is an expert in paleoanthropology, conducting research on the origins of mankind.

Rodents are widely distributed around the world.

He is an expert in paleoanthropology, investigating archaeological sites around the world.

He is famous as a countertenor singer.

Odd-toed ungulates include mammals such as horses and camels.