Polite form of apology with tense form?


After missing an appointment, which would be more appropriate for asking for
forgiveness or apologizing?

> ごめんなさい でした

or

> 本当にごめんね。ほんとうに ごめんね

In particular, considering the difference between the two, which would be
better to use for a 先生?




In this context, the best is:

> > 申｛もう｝し訳｛わけ｝ありませんでした。 I'm very sorry (lit. 'there was no excuse').

