Molecular weight of water is $$20$$ u.
The correct option is B False
Molecular formula of water is $$H_2O$$
Atomic weight of $$H$$ is $$1$$ u and of $$O$$ is $$16$$ u
Molecular weight of water =
$$2\times mass\ of\ H+1\times mass\ of\ O$$
$$2\times 1 + 16=18$$ u
Therefore, option $$B$$ is correct.