Step 1: Understanding colonialism in Doyle's writings.
Colonialism in literature often appears as themes related to imperialism, exotic places, and influences on British culture. In the context of Doyle's works, it can be seen in references to foreign lands, practices, and objects, as well as the fears and desires related to the unknown.
Step 2: Analysis of options.
(A) Opium dens in London, frequented by Holmes: Opium was associated with colonial territories and was a symbol of the perceived moral decay linked to British imperialism. The opium dens reflect colonial influence in urban Britain.
(B) The war in which Watson served as a doctor: Watson’s military service in Afghanistan connects to the British colonial presence in India, reflecting colonial conflicts.
(C) The hound in {The Hound of the Baskervilles:} This is a symbol of British fears, but it does not explicitly relate to colonialism as the other options do.
(D) The pet animals in “The Adventure of the Speckled Band”: Exotic and mysterious animals in the story may suggest colonial influences, as they often represent the unknown or foreign.
Step 3: Conclusion.
The options (A), (B), and (D) are related to colonialism in their depiction of foreign influences, while (C) focuses more on psychological fear rather than colonialism.
Final Answer: (A), (B), (D)