Which mixture is used for respiration by deep sea divers?

Scuba divers must cope with high concentrations of dissolved gases while breathing air at high pressure, underwater. Increased pressure increases the solubility of atmospheric gases in blood. When divers come towards surface, the pressure gradually decreases. This called bends. To avoid bends, the tanks are used by scuba divers that are filled with air diluted with helium (11.7% helium, 56.2% nitrogen and 32.1% oxygen). Thus, option $\left(\mathrm{d}\right)$ is correct.