The correct answer is 3. Nostromo because the characters mentioned—the Gould couple, Decoud, and the setting of Costaguana—appear in Joseph Conrad's novel Nostromo.
Explanation:
Gould Couple: Charles Gould, a wealthy Englishman, and his wife Emilia are central characters in Nostromo. Charles Gould is the owner of the San Tomé silver mine, a key element in the story.
Decoud: Martín Decoud is another significant character in Nostromo, known for his role in the political intrigue in the fictional South American country of Costaguana.
Costaguana: This fictional country serves as the backdrop for Nostromo. It is portrayed as a politically unstable South American republic, reflecting Conrad's themes of imperialism and corruption.
Other Options:
Victory: This novel by Conrad is set in the East Indies and revolves around Axel Heyst and Lena, with no connection to Costaguana or the characters mentioned.
Under Western Eyes: Set in Russia and Switzerland, this novel focuses on political ideologies and espionage, not South America or the Gould couple.
The Nigger of the Narcissus: This is a sea story focused on the crew of the ship Narcissus, with no relation to the characters or setting in the question.
Thus, Nostromo is the only novel that fits the description, making it the correct answer.