Option C is the correct answer because “COLLEAGUE” is the correct way to spell the word that means an official partner in any event, hence it is correct.
Option A is incorrect because ‘harassed’ is spelled correctly, it means making too many demands.
Option B is incorrect because ‘diagnose’ is spelled correctly, which means to arrive at a conclusion about a problem or a disease.
Option D is incorrect because” dialogue” is spelled correctly, it means a line or feeble lines used to convey a message.