Answer:
They sound familiar to Billy.
Step-by-step explanation:
Roald Dahl's short story "The Landlady," tells the unfortunate tale of how Billy Weaver, who was sent to Bath for business. In his eagerness to find a reasonable accommodation for the night, he ended up at the landlady's "Bed and Breakfast".
The weird thing about the lodging was that the landlady made her guests sign the guest-book and then poison them. Afterward, she'd stuff them and keep them as a prized collection. Likewise, Billy was asked to sign the book when he discovered that he felt the names sound so familiar to him. The names "Christopher Mulholland from Cardiff [. . .] Gregory W. Temple from Bristol" all sounded so familiar to him because they had appeared in the newspapers.
Thus, the correct answer is the fourth option.