"Mass can neither be created nor destroyed" is the statement of

Which of the following pairs of substances illustrates 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

Statement $1$: The mass ratio of hydrogen to oxygen in water obtained from rivers,wells,lakes,or seas is always $1:8$.
Statement $2$: In $1799$,the scientist Joseph Proust proposed the Law of Definite Proportions.

Two compounds are formed by carbon and oxygen. In one compound,the percentage of carbon is $42.9\%$ and in the other,the percentage of carbon is $27.3\%$. Which law of chemical combination is illustrated by this data?

Complete combustion of $0.66 \ g$ of a hydrocarbon gives $1.32 \ g$ of $CO_2$ and $2.7 \ g$ of water. The results of the given data follow the law of ...