Answer:
The first fish "appeared" on Earth about 500 million years ago. Up till now, more than 20,000 kinds of fish "have been named" and "described" by scientists. New species "are discovered" every year, so the total increases continually.
Hence, the correct answer is choice B., or appeared/ have been named/ described/ are discovered.
The first fish appeared on Earth about 500 million years ago. Up till now, more than 20,000 kinds of fish have been named and are discovered by scientists.
New species are discovered every year, so the total increases continually.
A species is a group of the same animals that can reproduce with each other.
Species are divided into 7 basic categories by Wilkins.
Here, there is species of fishes are given, saying that fishes appeared on earth about 500 million years ago.
Thus, the correct option is b.
Learn more about species
https://brainly.com/question/13259455
