Final answer:
A pop ballad is correctly described as slow and expressive, aligning with its historical roots and musical qualities such as rhythm, narrative storytelling, and emotional depth.
Step-by-step explanation:
The description of a pop ballad as slow and expressive is essentially true. Pop ballads typically have a slower tempo, allowing the vocalist to convey deep emotions and tell a story, which is why they are termed 'expressive'. This emphasis on storytelling and emotion aligns with the historical roots of ballads, which were originally used to transmit stories orally, often set to music. The word 'ballad' itself is derived from the Latin word 'ballare', which means 'to dance', pointing to the rhythmic quality integral to this form of music. Although the structure may vary, the essential features of a ballad that include its rhythm, narrative quality, and usually a rhyme scheme such as iambic tetrameter alternating with iambic trimeter, remain central to its definition and presence in popular music.