Which form of the word: "obligate" will fit in the sentence (ii) 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 phrase 'under no obligation' is a standard idiomatic expression meaning 'not required or bound to do something.' 'Obligation' is a noun, which is grammatically correct here. 'Obligate' is a verb, 'obligatory' is an adjective, and 'obligated' is a participle - none of which fit the noun position required after the preposition 'under no.'