Alliteration is the repetition of the same consonant sound in initial position in a series of words.
So, the correct answer here is B (Great is the Golden Cat who treads) as the sound "G" is repeated in the words "great" and "golden".
In answers A, C and D no consonant sound in initial position is repeated, so there is no example of alliteration.
Supposed*
You had a grammatical error and I had to fix it considering you’re an English teacher.
John H. Watson, known as Dr. Watson, is a fictional character in the Sherlock Holmes stories by Sir Arthur Conan Doyle. Watson is Sherlock Holmes' friend, assistant and sometime flatmate, and the first person narrator of all but four of these stories.
I feel like the answer is "his mother was a Christian and his father was a pagan"