Question

what were sextants, which used celestial bodies like stars to plot courses of movement and exploration, used for?
navigation
fusion
emission lines
parallax

Explanation:

Astronauts and early - navigators used celestial bodies like stars for navigation. Navigation is the process of plotting courses of movement and exploration. The other options (fusion, emission lines, parallax) are not related to using stars for plotting movement and exploration.

Answer:

navigation