Who kidnaps Buck and sells him into the Klondike gold rush?

The correct answer is Manuel, the gardener. Buck is a prized dog who lives a comfortable life in California, but his world changes dramatically when he is kidnapped by Manuel, who is in need of money to pay off a gambling debt. Manuel’s actions set off a chain of events that lead to Buck being sold into the brutal, demanding environment of the Klondike gold rush, where he is forced to adapt to a life far removed from his previous comforts.

This choice accurately reflects the pivotal moment in Buck's journey as he is ripped from his home and thrust into a harsh reality filled with struggle and survival. The other options, such as John Thornton, Spitz, and a gold miner, are significant characters in the story but do not play a role in kidnapping Buck. John Thornton is a key figure later in Buck’s life; Spitz is Buck's rival as a lead dog; and while a gold miner represents the environment Buck is sold into, none of them are responsible for Buck's initial kidnapping.