。
Is she home?
Literal
She [topic-は] home [at-に] is [question-か]?
About as basic as a Japanese question gets. The verb いる ('be, exist') is for animate beings (people, animals) — distinct from ある, which covers inanimate objects. The に marks location of existence: 家にいる = 'be at home.' Add ~ます for politeness and か for the question, and you get a textbook-clean polite question. The kind of thing you'd say on the phone or to someone at the door.