The correct option is D relatively
The sentence is about an exam paper that was easy "this year", and "this year" suggests that it's in mentioned in relation to the previous year. So, we use an adverb that most appropriately completes the sentence. 'Relatively' means 'in relation to'. When placed in the sentence, it means 'in relation to last year', since this completes the sentence in meaning, option C is correct. 'Effectively' means 'to accomplish the expected result', it's not relative to what the sentence means, hence option A is incorrect. 'Literally' means 'in a literal sense, from word to word', this isn't relevant to the sentence hence option B is incorrect. Option D is incorrect because this word does not exist in the English dictionary, nor is it used in Standard English.