We need to first come up with a balanced equation:
→ 
We know that the molar ratio of hydrogen to oxygen to water now is 4:1:2.
Converting the amount of grams given to moles is as follows:
Hydrogen: 
Oxygen: 
We know now that the limiting reactant is oxygen. We can then know that the number of moles of water are produced are double the number of moles of oxygen used due to the ratio that we established at the beginning - 4:1:2.
So we now can use 6.25 moles of water as the amount produced.
Then we convert moles of water to grams:

Now we know that there are 112.59g of water produced when we start with 50g of hydrogen and 50g of water.
Answer:
option A= Physical change
Explanation:
physical change:
" It is a change in which no new substance is formed"
Breaking of object like glass is the example of physical change because it is not change into another object. It effect the form of object but can not change the chemical composition.
Chemical changes:
" it is a change in which one substance is converted into new product through chemical reaction".
During the chemical changes the types and the number of atom remain same but their arrangement changed.
for example: burning of wood, baking of cake, digesting food, resting of iron etc.
Physical reaction:
" physical reaction occur during the molecular rearrangement. There is no chemical change occur"
In this type of changes no bonds are break to form new bonds, for example boiling point.
Chemical reaction:
" chemical reaction occur when molecules are chemically react with each others and bonds formation and breaking is also occur"