Which of the following works of Milton seeks to adapt the form of Greek tragedy?

The correct option is Samson Agonistes.

John Milton's Samson Agonistes (published in 1671 alongside Paradise Regained) is a closet drama that was explicitly written to adapt the form and conventions of classical Greek tragedy.
In the preface to the work, titled "Of That Sort of Dramatic Poem Which Is Called Tragedy," Milton defends the tragic genre and outlines his intention to follow the model of Greek playwrights such as Aeschylus, Sophocles, and Euripides.
Specifically, Samson Agonistes conforms to the classical Aristotelian unities of action, time, and place: the action occurs in a single location (before the prison in Gaza), spans less than a day, and maintains a single focused plot. It also employs a chorus, which is a defining feature of ancient Greek tragedy.