Select the most appropriate option to fill in the blank.
I didn't attend the marriage _______ he didn't invite me.

Correct option is C

The correct option to fill in the blank is (c) because.

Explanation:
The sentence requires a conjunction of reason. The second clause ('he didn't invite me') explains why the action in the first clause ('didn't attend') happened. 'Because' is the appropriate conjunction.

Example: I stayed home because I was feeling unwell.

Information Booster:
'Because' introduces a reason, 'so' introduces a result, 'but' introduces contrast, and 'however' is an adverb used to show contrast.

So the correct answer is (c)