Bilbo finds in the passageway when he comes to after being knocked out by a goblin.

When Bilbo regains consciousness, he can see nothing in the darkness. Feeling around on the floor, he happens to come across a ring, which he puts in his pocket. He has no idea where the rest of the company is, or in which direction the exit lies. Picking the path he feels he had been traveling with the dwarves, he soon comes across an underground lake. There, he discovers a strange creature named Gollum. When Gollum sees Bilbo prowling around, obviously lost, he is interested and a bit hungry, so he approaches the hobbit.

(the answer is d)

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