What finally makes odysseus mad at penelope?
she refuses to recognize him.
it appears to him that she forgot the bed won't move.
she is angry at odysseus for killing the suitors.
she forgot the "secret signs" that only the two of them know.

It appears to him that she forgot the bed won't move.

Explanation:

Penelope is acting weirdly since many impostors showed up claiming to be Odysseus and many suitors showed up at her house, annoying her. She wanted to make sure that Odysseus was really Odysseus, so she asked for a servant to move his bed, but Odysseus finally speaks out and claims that it is impossible and only a good could do that.