The correct answer is functioning for the State. Key Points In the sentence, 'functioning for' is incorrect. Here, the preposition 'for' is used for saying who or what is intended to receive something or get the benefit of it. The preposition 'of' means belonging to somebody; relating to somebody. In the sentence, parliamentary democracy is related to the State. So, 'of' must be the correct preposition. So, 'functioning for the State' is the correct solution. Hint In error-type questions, we first look for grammatical errors if any and then vocabulary based errors. We look at the tense of the whole sentence and see if all the verbs are in the correct tense. So the correct sentence is - One could argue that these are the compulsions of parliamentary democracy for the smooth functioning of the State.