The exosphere is the outermost layer of the Earth`s atmosphere, extending from about 500 km above the Earth`s surface to the edge of space. In the exosphere, the gases are very sparse and there is no clear boundary between the atmosphere and space.

Among the options given, the gas found in the highest quantity in the exosphere is hydrogen. Hydrogen is the lightest and most abundant element in the universe. In the exosphere, hydrogen atoms are very sparse and can travel freely without colliding with other atoms. These hydrogen atoms are also the ones that can escape Earth`s gravity and enter space.

Helium, on the other hand, is the second most abundant element in the universe but is found in smaller quantities in the Earth`s exosphere compared to hydrogen. Nitrogen and oxygen, which are the two main gases in the Earth`s lower atmosphere, become less abundant as we move higher up in the atmosphere and are found in even lower quantities in the exosphere.

Therefore, the correct answer is option 1: Hydrogen is found in the highest quantity in the exosphere.