An atom's mass number equals the number of protons plus the number of neutrons.
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Answer:
thermodynamics
Explanation:
The laws of thermodynamics define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium.
Solution= The answer is true
Elliptical and Spiral have some similarities, they both are huge and contain lost of dust and also they are held by gravitational forces.