In the decomposition of water, why is twice as much hydrogen as oxygen formed?

Question

Responses

There are two atoms of hydrogen and one atom of oxygen in a water molecule.
Some oxygen gas escapes the reaction, and hydrogen gas is conserved.
Hydrogen gas has two atoms, and oxygen gas has one atom.
Hydrogen atoms are twice the size of oxygen atoms.

Answer 1

There are two atoms of hydrogen and one atom of oxygen in a water molecule.