Question

The fourth state of matter is:
A. solid
B. fluid
C. liquid
D. plasma

Answer 1

Hint: The main three states of matter are solid, liquid and gas and fluid is something that has the ability to flow. So, liquid and gas both are fluid. So, fluid is not the state of matter. A fluid is a common term used for both liquid and gas as they both can flow.

Complete step by step answer:
In this question we have asked what is the fourth state of matter? As we know matters have 3 main states- solid, liquid and gas. Except these three states we have 2 other states of matter which are plasma and the other one is human- made Bose-Einstein condensates. So, we can say the fourth state of matter is plasma and fifth is Bose- Einstein condensate. Plasma is a hot ionized gas which contains an equal number of positively charged ions and negatively charged electrons and it's not a gas because its characteristics are different from ordinary gas.
We can call it a subset of gases. The example of plasma is the excited low-pressure gas inside neon signs and fluorescent lights, solar wind, welding arcs.
We have four options solid, fluid, liquid and plasma. So, solid and liquid are the first three states of matter and as we already mentioned that fluidity is not the state of matter. Fluidity is the ability to flow. So, liquid and gas both are fluid.
So, the correct option will be D. Plasma

Note:
Plasma is used in TV, fluorescent lights and neon signs. Aurora, stars and the lightning and some flames consist of plasma.Plasma, in physics, an electrically conducting medium in which there are roughly equal numbers of positively and negatively charged particles, produced when the atoms in a gas become ionized. It is sometimes referred to as the fourth state of matter, distinct from the solid, liquid, and gaseous states.