This is an analogy question — look for a relationship between the first pair and match it to the second.
Consider the second part: word : sentence. A “word” is a part of a “sentence”.
Now apply the same logic: A “spoke” is a part of a “wheel”.
Other options:
(A) Speaker – not related to "spoke" in the mechanical sense.
(B) Paragraph – not logically connected.
(D) Comma – not related to “spoke”.