Q: There are about 50,000 vertebrate species, and they are placed in how many different classes?


Read this paragraph and choose the correct option from the provided answers:

There are about 50,000 vertebrate species, and they are placed in nine different classes. Five of the classes are fish. The other classes are amphibians, reptiles, birds, and mammals. Table below lists some of the distinguishing traits of each class.

 Choices:

- four

- ten

- three

- nine


A:
nine