💡 Detailed Explanation
The speaker is making a very formal apology using the set phrase '私の不徳の致すところ' (due to my lack of virtue/my own failing). This is a way of taking full responsibility. The most appropriate response from a superior or colleague is to soften the blame, not to agree harshly or ask for the meaning of the formal phrase. Response 1 shows understanding and shares the burden, which is a common and natural reaction in a Japanese workplace.