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What element makes up water?

  1. Hydrogen

  2. Oxygen

  3. Nitrogen

  4. Helium

The correct answer is: Hydrogen

Hydrogen is the correct answer because it makes up about 2/3 of the atoms in water. Oxygen, on the other hand, makes up the remaining 1/3 of atoms in water. Nitrogen and Helium do not make up any part of water, making them incorrect choices. While Nitrogen is also a gas like Oxygen, it does not bond with Hydrogen to form water molecules. Helium, on the other hand, is a noble gas and does not interact with other elements to form compounds like water. Therefore, A is the only correct option.