Question

The first person in the door was she.A.predicate nominativeB.object of a prepositionC.subjectD.direct object

Answer 1

The first person in the door was she.A.predicate nominativeB.object of a prepositionC.subjectD.direct object

The first person in the door was she. The answer is letter B. The object of preposition.

Answer 2

You didn't underline or italicize anything.

The first person would be a predicate nominative.
The door would be object of a preposition.
She would be a subject.