What is the celestial sphere?

A. The celestial sphere is a representation of how the entire sky looks as seen from Earth.
B. The celestial sphere is a model that shows the true locations in space of the Sun and a few thousand of the nearest stars.
C. The celestial sphere is a model of how the stars are arranged in the sky relative to our Sun, which is in the middle of the sphere.
D. It represents a belief in an Earth-centered universe, and hence is no longer considered to have any use.

A. The celestial sphere is a representation of how the entire sky looks as seen from Earth.

Explanation:

The celestial sphere is an imaginary sphere that has an arbitrarily large radius and is concentric to the earth. It is an abstract spherical shell formed by the sky usually represented as an infinite sphere, the center of which is a given observer's position (earth). It's represents how the sky looks from the observer's position (Earth).

when a device is used in a circuit in which the voltage is 81 v, the current flowing through the device is 3 a. what is the resistance of the device?

a. 27 ω

b. 40.5 a

c. 243 ω

d. 243 a

the correct answer is a. 27