Answer: Option (b) is the correct answer.
Step-by-step explanation:
Plasma is defined as the state of matter which is a hot ionized gas consists of positively charged ions and negatively charged electron.
For example, neon is a plasma as it is a gas that contains charged particles.
So, when a gas is further heated then a stage reaches where it becomes ionized and hence it then changes into plasma state.
Thus, we can conclude that the plasma state occurs when gases are heated.