Which of the following is used as a cooling medium for the Large Hadron Collider (LHC) and the superconducting magnets in MRI scanners and NMR spectrometers?

Correct option is D

The correct answer is (d) Helium.
Helium is used as a cooling medium for the Large Hadron Collider (LHC) and the superconducting magnets in MRI scanners and NMR spectrometers. Helium, particularly in its liquid form, has extremely low boiling points, making it ideal for cooling superconducting magnets to the temperatures required for their operation, which is typically just a few degrees above absolute zero. This cooling is essential for maintaining the superconducting state, which allows these magnets to operate efficiently and produce strong magnetic fields.
Therefore, the correct answer is (d) Helium.