Answer:
![2H_2+O_2\longrightarrow 2H_2O](https://img.qammunity.org/2020/formulas/chemistry/high-school/q8qqfyrbqf2nn5lvkcz1j02a9hr1cmoil2.png)
Step-by-step explanation:
Law of conservation of matter : It states that matter can neither be created nor be destroyed but it can only be transformed from one form to another form.
Balanced chemical reaction : It is defined as the reaction in which the number of atoms of individual elements present on reactant side must be equal to the product side.
A)
![Ca+Cl_2\longrightarrow CaCl](https://img.qammunity.org/2020/formulas/chemistry/high-school/kge4iv7qw9cem78bhqk0644eegzmle15mn.png)
B)
![Ca+Cl_2\longrightarrow Ca_2Cl](https://img.qammunity.org/2020/formulas/chemistry/high-school/94jg36rw47ingh735x0xblcvs8bci9pwuj.png)
C)
is correctly balanced as the number of atoms of hydrogen and oxygen are equal on the both side of the reaction.
D)