[Vocabulary] Must "first" be followed by "one" in a list?

[Buddy42]

Dear teachers,

there are three types of XY and I'd like to present them one after the other to an audience. Do I have to say:

Mr P. distinguishes three types of XY.

a) The first one is the hysterical.....

Or can I omit the "one" and say:

b) The first is the hysterical....

Thanks in advance

 

[emsr2d2]

Yes, you can.

I'd use "identifies" rather than "distinguishes". You can say that he distinguishes between the three types by ...