15. On 16 July your 1810 zone time DR position is LAT 24°16.5' S, LONG 162°52.0' E. Considering their magnitude, azimuth, and altitude, which group includes the three bodies best suited for a fix at star time?

Jupiter, Alphard, and Alphecca are the best choice because their altitudes and azimuths, when calculated for the given date, time, and DR position, produce strong, intersecting lines of position for an accurate three-body fix.