Jawaban:

O due to

Penjelasan:

The correct answer is C. due to.

A. Although-is used as a conjunction to introduce a contrast or concession, which would not be appropriate in this case.

B. Because-is used to express a reason or cause, which would be appropriate in this case, but it is a bit too casual for a formal message.

C. Due to-expresses a reason or cause, and it is often used in a more formal or professional setting, making it the most appropriate choice for a situation where the speaker is unable to attend an event.

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