The true answer is: It's conserved because the total number of H atoms on each side is 12.
the first two answer is wrong because it's conserved not as mentioned, It's not conserved.
and the last one also wrong because the total number of O atoms are equal at the two sides but not equal 2.
I think because its the only one to be liquid at normal temperatures.
Answer:
It's true.
Explanation:
In sub-energy level : number of orbitals

To find the third side you would use Pythagorean theorem which is a²+b²=c².
A and B being the 2 legs and C being the hypotenuse.
Example: ( sorry for the really odd not really a triangle, triangle...)
| \
6| \ ? 6²+9²=C²
|_______ 36+81=C²
9 117=C²
√117=10.8 (rounded)
if you need to get the leg you just fill in the numbers.
Always younger than the rock it intrudes