Statement (A) : The valency of  Fe in $\text{FeC}{l}_2$is 2 and that of $\text{FeC}{l}_3$ is 2

Statement (B) : In ${\text{Cu}}_{\text{2}}\text{C}{l}_{\text{2}}$ and $\text{CuC}{l}_{\text{2}}$the valency of Cu is 2 and 1 respectively.

Statement (C) : In $\text{SnC}{l}_2$and $\text{SnC}{l}_4$the valency of  Sn is 2 and 4 respectively.

In $\text{FeC}{l}_2$, valency of Fe  is 2 but in $\text{FeC}{l}_3$ valency of    Fe is 3

In ${\text{Cu}}_{\text{2}}\text{C}{l}_{\text{2}}$  and  $\text{CuC}{l}_{\text{2}}$, the valency of  Cu is 1 and 2 respectively.

 In $\text{SnC}{l}_2$ and $\text{SnC}{l}_4$ , the valency of  Sn is 2 and 4 respectively.

We know that the combining capacity of an element is called valency.

So, statements A and B are incorrect but statement C is correct.