Which of the following is the fifth state of matter?

Bose-Einstein condensates

The correct answer is option 4. Bose-Einstein condensates.

The fifth state of matter among the options provided is Bose-Einstein condensates.

Bose-Einstein condensates (BECs) represent a unique state of matter that occurs at extremely low temperatures near absolute zero (-273.15°C or 0 Kelvin). In a Bose-Einstein condensate, particles such as bosons (a type of subatomic particle) occupy the same quantum state and behave collectively as a single quantum entity. BECs exhibit unusual quantum phenomena, such as superfluidity and wave-like behavior, making them distinct from the classical states of matter like solids, liquids, gases, and plasmas.