Which form of the word: "obligate" will fit in sentence (i) given below? It is (i)that we finish our work by 4 pm. You are under no (ii)_to accept our proposal. The higher authorities were not only entitled, but also(iii)____, to take appropriate measures

The sentence needs an adjective to complete 'It is ___ that we finish our work'. 'Obligatory' is an adjective meaning required, compulsory, necessary - 'It is obligatory that we finish our work' correctly expresses necessity. 'Obligate' is a verb, not adjective. 'Obligated' is a past participle/adjective but means 'required to do something' used for people ('I was obligated'), not for impersonal it-clauses. 'Obligation' is a noun. Only 'obligatory' functions as adjective modifying the clause.