Which pronoun would correctly fill in the blank? 'Either folk songs or country songs are my favorite types of music because of _____ good rhythms.'

The correct choice to fill in the blank is 'their.' This pronoun effectively refers back to the plural noun 'types,' which is used in conjunction with the compound subject 'either folk songs or country songs.' In this context, 'their' indicates possession, acknowledging that the good rhythms belong to the favorite types of music mentioned.

Using 'their' aligns with the plural nature of 'types' and maintains grammatical consistency throughout the sentence. This helps to reinforce clarity and cohesion in communication. On the other hand, 'it's,' 'his,' and 'her' are singular forms and do not appropriately match the plural noun 'types' or the context in which they are used, making them unsuitable choices for this sentence.