The correct answer is (C) because a sentence is arrange in a formation which is (subject, verb and object) the subject is the doer of the action , the verb is the action (auxiliary + lexical/ main verb) and the object which is the receiver of the action.

I couldn’t help laughing = past continuous tense

Subject (I) auxiliary verb (couldn’t) hexical verb (help)

The other options are disarranged and not appropriate