。
Is she a doctor?
Literal
She [topic-は] doctor is [question-か]?
A textbook-clean polite yes/no question. ですか combines polite copula です with question particle か — the simplest interrogative form for nouns and な-adjectives. In casual speech the か often drops with rising intonation (彼女は医者?). The plain ですか makes no implicit assumption about the answer; the negative ~ではないのですか, by contrast, would carry an embedded expectation.