True lasers may consist of which states of matter?

True lasers can indeed consist of solid, liquid, and gas states of matter, making the first option the correct choice.

In solid-state lasers, a solid gain medium (such as ruby or Nd:YAG) is used, where the atoms within the solid are excited to produce laser light. Liquid lasers, often referred to as dye lasers, utilize a liquid gain medium that can be a dye dissolved in a solvent, allowing for tunable wavelengths based on the specific dye used. Gas lasers, like the helium-neon or carbon dioxide lasers, employ a gas as the lasing medium; the gas atoms or molecules are excited to produce coherent light.

This versatility across different states of matter is a significant aspect of laser technology, allowing for various applications and adaptations depending on the desired outcome, such as in medical treatments, industrial applications, and telecommunications.