Question

the line marked c in the celestial sphere diagram represents the _______.
○ south celestial pole
○ nadir
○ celestial equator
○ north celestial pole
○ zenith
○ ecliptic
○ horizon

Explanation:

To solve this, we recall the definitions of celestial sphere components:

• The celestial equator is the projection of Earth's equator onto the celestial sphere, a great circle midway between the celestial poles.
• The south/north celestial poles are points, not lines. Nadir/zenith are points (opposite of zenith is nadir, directly below/above observer). Ecliptic is the Sun's apparent path, horizon is the observer's local horizontal circle. The line marked C (assuming standard diagrams) representing a great circle midway between poles matches the celestial equator.

Answer:

celestial equator