As a Rule of Thumb,when Might an Evaluation by a Speech

As a rule of thumb,when might an evaluation by a speech pathologist be advisable?

A) If by age 4 the child's language is not understandable to people outside the family.
B) If by age 2 the child is not speaking in complete sentences.
C) If by age 2 the child has a vocabulary of less than 100 words.
D) If by age 3 the child has difficulty articulating "ch" and "sh" sounds.