Which of the following pairs of substances illustrate the law of multiple proportions?

The percentage of copper and oxygen in samples of $CuO$ obtained by different methods were found to be the same. This illustrates the law of

When two elements combine to form more than one compound,the masses of one element that combine with a fixed mass of the other element are in a simple whole number ratio.
$(a)$ Is the statement given above correct?
$(b)$ If 'yes',which law does it follow?
$(c)$ Give an example corresponding to this law.

Which of the following examples illustrates the Law of Multiple Proportions?

Explain the Law of Multiple Proportions.

$A$ chemical equation is balanced according to the law of