Answer:
Onomatopoeia.
Explanation:
Onomatopoeia is the literary technique used when words are formed based on the sounds they produce. In other words, onomatopoeia is when a word is formed from the sound it makes, like "hiss, buzz, wham, pop, bang" etc.
In the given line "And now he comes again with a clatter of stone" from Robert Frost's poem "The Runaway", the word "clatter" is the sound produced by the stones. Therefore, it is an onomatopoeic word.
Thus, the correct answer is onomatopoeia.
