Chemistry - Complete Pblock- Question with Solution | TestHub

Liquid helium (He(liquid)) is an excellent cryogenic agent due to its extremely low boiling point of 4.2 K ($-269$ °C). It is used to achieve ultra-low temperatures required for various scientific and industrial applications, such as cooling superconducting magnets in MRI machines and particle accelerators.

The final answer is $\boxed{He(liquid)}$.