Read the following passage from William Wordsworth's "The Solitary Reaper," then answer the question.
"A voice so thrilling ne'er was heard
In spring-time from the Cuckoo-bird,
Breaking the silence of the seas
Among the farthest Hebrides."
What is "the voice" to which Wordsworth refers?
A. an angel
B. a maiden
C. a lover
D. a bird