Final answer:
In 'The Mixer' by P.G. Wodehouse, the shy man, Mr. Budlong, bought Blackie to guard his house, making option B the correct answer.
Step-by-step explanation:
The shy man bought Blackie in the story 'The Mixer' to guard his house. The correct answer to why the shy man, Mr. James Clarence Budlong, bought Blackie is option B. In the story by P.G. Wodehouse, Mr. Budlong, who is described as a man with little courage, needed a guard dog to protect his property from potential burglars. He believed that Blackie, despite his friendly and sociable temperament, would serve this purpose. However, the shy man got much more than a guard dog as Blackie turned out to be quite a character with his own thoughts and narrative of the events.