Answer:
If my friend calls, tell them I'm at my violin lesson.
Step-by-step explanation:
Inappropriate shift in number can be regarded as an error that is associated with pronoun use. It can be explained as the distinction associated with count of either pronouns or nouns.
From two distinctions in English , Noun can be a singular (one) or plural ( more than one). From Concord agreement, their must be an agreement between the pronouns and their anticidents with regards to the distinctions above. i.e a singular pronoun takes a singular anticidents, while a plural pronouns take a plural anticidents.