Scuba divers are at risk due to the high concentration of dissolved gases while breathing air at high pressure underwater. The tanks used by Scuba divers are filled with various gases to allow them to breathe while diving.

Option 1 states that the tanks are filled with air diluted with Helium. Helium is often used in diving to reduce the amount of nitrogen in the breathing mixture. This helps to prevent nitrogen narcosis, a condition that can occur when too much nitrogen is consumed at depth and can cause confusion and impaired judgment.

Option 2 states that the tanks are filled with Oxygen (O2). While oxygen is a crucial component for respiration, it is not used as the primary gas in scuba diving tanks. Breathing pure oxygen at depth can be dangerous and cause oxygen toxicity.

Option 3 states that the tanks are filled with Nitrogen (N2). While nitrogen is present in the breathing mixture, it is not used as the sole gas in the tanks. Breathing air with a high concentration of nitrogen at depth can lead to nitrogen narcosis.

Option 4 states that the tanks are filled with a mixture of Nitrogen and Helium. This is partially correct, as helium is often added to the breathing mixture to reduce the nitrogen content. However, helium is