Answer: B : There are two hydrogen atoms.
Explanation:In chemical reactions, symbols and formulas represent the substances that are formed or broken down. The formula for water is H2O.
The symbols H and O mean that water contains the elements hydrogen and oxygen. The subscript 2 shows that there are 2 hydrogen atoms in a molecule of water.
Since there is no number beside the O, there must be only one oxygen in the water molecule.