Answered

which sentence shows correct subject- verb agreement?
A. My friend and her mother were listening to the radio.
B. My friend and her mother was listening to the radio.



Answer :

A is correct because "my friend and her mother" can be substituted by the pronoun "they" which is plural, therefore the plural verb needs to be used, which is "were".
A  is correct. this is because more than one person was listening to the radio (my friend AND her mom) so you would use were as a plural tense rather than was because was refers to only one person using the radio.
i hope this helped!!!!