Final Answer:
In Agatha Christie's novel "And Then There Were None," the discovery made when it is decided to lock up the remaining weapons is D) The missing key to the weapons.
Step-by-step explanation:
In a crucial moment of suspense within the narrative, the characters in "And Then There Were None" decide to secure the remaining weapons, a sensible precaution given the mysterious murders occurring on the isolated island.
The missing key to these weapons becomes a significant revelation, intensifying the sense of mystery and suspicion among the characters.
This discovery plays a pivotal role in the plot, raising questions about the identity of the murderer and the level of trust among the dwindling group of characters. The missing key becomes a symbol of the hidden truths and uncertainties that permeate the story, adding layers of complexity to the unfolding mystery. Agatha Christie masterfully employs this plot device to maintain suspense and keep readers engaged as they navigate through the twists and turns of the narrative. OPTION D