The altitudes of a circumpolar star at culminations are 70° and 10°, both culminations being north of zenith. The declination of the star, is A. 80° B. 70° C. 60° D. 50°

The correct answer is $\boxed{\text{B}}$.

The altitude of a star is the angle between the horizon and the star. The declination of a star is the angle between the star’s celestial equator and the observer’s horizon. A circumpolar star is a star that never sets or rises for an observer at a given latitude.

At culmination, a star is at its highest point in the sky. For a circumpolar star, the altitude of the star at culmination is equal to the star’s declination. In this case, the altitudes of the star at culmination are 70° and 10°, so the declination of the star is