Question

read the source of the allusion.
in herman melvilles classic novel moby - dick, captain ahab is fixated on his goal of tracking down and getting revenge on a white whale.
what is the meaning of the allusion in the sentence below?
the detective spent his career chasing his white whale, a notorious bank robber who had eluded law enforcement for decades.
an object of obsession
a clever criminal

Explanation:

In Moby - Dick, Captain Ahab is obsessed with the white whale. In the given sentence, the detective's "white whale" (the bank robber) is what he is fixated on throughout his career. The allusion here is to the object of obsession (like Ahab's obsession with the whale), not just a clever criminal (the description of the robber is additional, but the allusion's core meaning is from the obsession aspect).

Answer:

an object of obsession