Water is always made up of part hydrogen to oxygen by mass.

The formula of water is . Thus, molar ratio is 2:1.

Thus,

Number of moles are related to mass and molar mass as follows:

Here, m is mass and M is molar mass

Molar mass of hydrogen is 1 g/mol and that of oxygen is 16 g/mol

Converting molar ratio into mass ratio as follows:

Also,

Putting the values of molar mass,

Thus,

Thus, water is always made up of 32 part hydrogen to 1 part oxygen by mass.

i think it's letter a.