You are researching the development of the telephone. You find a forum on the web from random English teachers who log in with made-up names. They rant about how texting is ruining this generation's written communication skills. This source is:

This source can be described as a primary resource. English teachers are professionally experts on the field of grammar, sentence structuring, punctuation and all the principles that guide the language. Hence, they can be good participants to ask this opinion from.