Which is the best way to describe the rhythm of “The Ballad of Birmingham”?

The stanzas with dialogue are more like free verse, but the stanzas spoken by a narrator are in iambic pentameter.

The poem does not follow a strict pattern of rhythm, but most lines contain three or four feet of meter.

The poem is written in free verse, but repeated refrains create a pattern of rhythm from time to time.

Every line in the poem has the same iambic pentameter pattern of rhythm.