Final answer:
Plasma is the least common phase of matter on Earth.
Step-by-step explanation:
The least common phase of matter on Earth is plasma. Plasma is often referred to as the fourth state of matter, after solids, liquids, and gases. It is a highly ionized gas composed of positively and negatively charged particles. Plasma is commonly found in high-temperature environments such as stars, lightning, and certain types of flames.
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