If the Sun's observed altitude is 47°50', the zenith distance is __________.

Correct Answer: Option A — 42°10'

Zenith distance is defined by Bowditch as the angular distance from the celestial body to the observer's zenith, calculated by subtracting the observed altitude (Ho) from 90°00'. Subtracting 47°50' from 89°60' leaves 42°10'.