What is the volume ratio for hydrogen to oxygen in water? $\left(2:1 / 1:2\right)$

At what temperature does water change into steam?

$$\begin{gathered} \mathrm{A}: {100}^{\circ }\mathrm{C} \\ \mathrm{B} : {60}^{\circ }\mathrm{C} \\ \mathrm{C} : 0^{\circ }\mathrm{C} \end{gathered}$$

Enter your correct as $\mathrm{A}, \mathrm{B} \mathrm{or} \mathrm{C}$.

At what temperature is the density of water maximum? 

$$\begin{gathered} \mathrm{A}: {100}^{\circ }\mathrm{C} \\ \mathrm{B} : 0^{\circ }\mathrm{C} \\ \mathrm{C} : 4^{\circ }\mathrm{C} \end{gathered}$$

Enter your correct as $\mathrm{A}, \mathrm{B} \mathrm{or} \mathrm{C}$.

Name the largest source of water on earth?