after discovering that the hobbits are missing , Aragon says "An evil choice is now before us " What is the choice they must make, and why is it evil?

They have the choice of burying their dead and following the Orcs to see if any of their men are being held captive or seeking Frodo. The choice is evil because either way they let someone down. Aragorn had pledged himself to Frodo.

'Let me think!' said Aragorn. 'And now may I make a right choice and change the evil fate of this unhappy day!' He stood silent for a moment. 'I will follow the Orcs,' he said at last. 'I would have guided Frodo to Mordor and gone with him to the end; but if I seek him now in the wilderness, I must abandon the captives to torment and death. My heart speaks clearly at last: the fate of the Bearer is in my hands no longer. The Company has played its part. Yet we that remain cannot forsake our companions while we have strength left. Come! We will go now. Leave all that can be spared behind! We will press on by day and dark!'