Answer:
D: By silver reeds in a silver stream
Step-by-step explanation:
The figure of speech Alliteration ("letters of alphabet") is a stilistic device, and it is defined by the repetition of the sound of the initial letters in a sequence of words (it can be consonants or vowels, or even different letters that have the same sound. Example: Phillip's feet ). In the poem, the words in option D present alliteration with the repetition of the sound s : silver; stream.