In Daphne Du Maurier's short story, "The Birds," the main character is Nat Hocken, who lives with his wife and two children on "the Cornish coast of England."
Wounded in the war, and compensated by way of a pension, Nat supports his family by working part-time at the Triggs, a neighboring farm.
Nat has a reputation of keeping to himself—described as a "solitary" person. He is observant and notices the birds gathering, as well as their unusually aggressive behavior. It is perhaps because he is so much on his own that he sees what his neighbors do not. After the first night defending his family and home from the attacks of the birds, he notices (going outside) that no smoke is rising from the fireplaces of homes in town, and when visiting the Triggs' farm, he find Mr. and Mrs. Trigg dead, as well Jim, their hired hand.
If I were to choose one answer, I would select "unnecessary." Though his interactions with the Triggs is "placid" (calm), Nat's disposition seems to lean more closely to "unnecessary." He is an efficient worker, but seemingly introspective and quietly observant. The other choices do not seem to fit at all. As the family is very closely knit, I believe this description could apply to both Nat, and his wife and children. ("Imperative" means "absolutely necessary," and "furtive" means "sneaky.")