Subscripts in the chemical formula X2Y3 denotes:
A. 2 atoms of X combine with 3 atoms of Y to form X2Y3
B. The subscript 2 denotes that valency of X is 2.
is true and B is false.
The subscript 2 denotes that valency of Y is 2. And that of X is 3. Because when we write the formula we cross multiply the valencies