Choose the most appropriate words/phrases to complete the letter

Dear Mr Wilson,

I am writing to [apologise for|say I'm sorry][letting you down|failing you]. I know I had promised to water your plants while you were away on holiday, but an opportunity came up that I could not miss.

As you [were aware|knew], I had been looking for a summer job for quite some time. To my delight, I found one the day after [your departure|you left]. My mother's brother was visiting when he [said|mentioned] that the amusement park near his town was looking to [hire|fill some positions] for the summer. As my uncle lives in the countryside, it meant staying with him all summer, which was [all right by me|a most welcoming offer]. I asked my brother to continue the watering for me but, unfortunately, he proved to be quite unreliable.

I understand that some of your plants were destroyed by the heat. [To compensate|To make it better], I would like to pay for any plants that will [require|need] to be replaced.

Please accept my apology again.

[Yours sincerely|Yours],

Albert Jones