Agroup of stars, gas, and dust held together by gravity is a
a. galaxy
c. local group
b. constellation
d. both a and b

the correct answer is Option a.

Explanation:

Galaxy is defined as the collection of stars, dust and gases which are held together by gravity. For Example: Milky way is a collection of more than 200 billion stars.

Local Group is defined as the collection of galaxies which include Milky Way.

Constellation is defined as the group of stars which form an imaginary pattern. For Example: Orion, Leo etc..

From the above information, the correct answer to this question is Option a.

a

Explanation:

Idk why

32: from largest to smallest, this hierarchy includes eons, eras, periods, epochs, and ages.

33: answer is c

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explanation:

physics means: "the branch of science concerned with the nature and properties of matter and energy. the subject matter of physics, distinguished from that of chemistry and biology, includes mechanics, heat, light and other radiation, sound, electricity, magnetism, and the structure of atoms."