。
Can you reach the top of the bookshelf?
Literal
Bookshelf [attributive-の] top [at-に] hand [subject-が] reaches-[polite]-[question-か]?
手が届く ('hand reaches,' a set expression for 'to be within reach') is used here literally, asking whether the listener can physically reach the top shelf. The expression also has a common figurative use — 'affordable,' 'attainable.' に here marks the target location. 届く ('to arrive, reach') is intransitive and takes its subject (the hand) with が.