None of the provided sentences contain a clear example of alliteration, which is the repetition of the same initial consonant sound in closely placed words. However, if modified for your options, consider that the sentence "The pretty purple petals of the flowers made the arrangement beautiful" has some alliteration with the repeated "p" sound in "pretty," "purple," and "petals."
So, the sentence that best demonstrates alliteration is:
The pretty purple petals of the flowers made the arrangement beautiful.