There are many figures of speech that use repetition:
Rhyme - Repeating sounds at the end of words.
Alliteration - Uses repetition of a specific consonant sound at the beginning of words or syllables.
And many more! But these are basic ones that you might be referring to.
B, “They saw the concert in the park last weekend.”
A concert in the park can be considered by some a “full” noun, or have a be a modifier, but both are correct.
It should be the letter A for yor answer
I'd say B, since a sentence fragment is just an incomplete sentence that's usually separating the sentence from it's main clause.
