The correct options are
A In gas-cooled nuclear reactors
C In NMR spectrometers and MRI systems
D As a diluent for oxygen in modern diving apparatus
Helium is used
- in filling balloons for meteorological observations.
- in gas-cooled nuclear reactors.
- as cryogenic agent for low-temperature experiments.
- to produce and sustain powerful superconducting magnets of modern NMR spectrometers and Magnetic Resonance Imaging (MRI) systems for clinical diagnosis.
- as a diluent for oxygen in modern diving apparatus because of its very low solubility in blood.