💡 Detailed Explanation
The correct choice is 'くれ' (from 'くれる' - to give to me/my inner circle). The grammar pattern '[Verb Te-form] + くれる' indicates that someone else did a favor for the speaker, structured as '[Giver] が 私に [Verb Te-form] くれる'. Sentence translation: 'On my birthday, my friend sent me a present by mail.' 'あげ' (to give to others) would mean the speaker gave it to the friend. 'もらい' (to receive a favor) would require the particle 'に' after the friend ('友達に...もらいました'). 'やり' (to give to animals/plants/juniors) is inappropriate.