Mockingbirds have no song of their own, but it can imitate up to a hundred other birdcalls.

Northern mockingbirds, year-round residents of the Bay Area (having expanded their breeding range here after the arrival of European settlers), each develop their own songs. Similar to those of other songbirds, mockingbirds’ songs consist of a specific configuration of syllables and phrases, sung primarily to court a mate or defend a territory. However, northern mockingbird songs are different from most of the world’s other 5,600 songbirds’ in that they consist of brief imitated phrases strung together and sung repeatedly—sometimes as many as a dozen times.

the question is the text structure of this passage is. a. chronological order. b. problem and solution. c. cause and effect. d. compare and contrast.