Which of the following statements indicates that law of multiple proportion is being followed?

Options

A. An element forms two oxides, XO and `XO_2` containing 50% and 60% oxygen respectively. The ratio of masses of oxygen which combines with 1 g of element is 2 : 3.
B. Hydrogen sulphide contains 5.89% hydrogen, water contains 11.1% hydrogen and sulphur dioxyde contains 50% oxygen.
C. 3.47 g of `BaCl_2` reacts with 2.36g of `Na_2SO_4` to give 3.88 of `BaSO_4` and 1.95 g of NaCl.
D. 20mL of ammonia gives 10 volumes of `N_2` and 30 volumes of `H_2` at constant temperature and pressure.

Explanation

To determine which statement indicates that the law of multiple proportions is being followed, we need to understand the law itself. The law of multiple proportions states that when two elements combine to form two or more different compounds, the masses of one element that combine with a fixed mass of the other element will be in the ratio of small whole numbers.

Let's analyze each option step by step:

### Step 1: Analyze Option A
- **Statement**: An element forms two oxides, XO and XO2, containing 50% and 60% oxygen respectively. The ratio of masses of oxygen, which combine with one gram of the element, is 2:3.
- **Analysis**:
- Here, we have two compounds formed by the same elements (X and O).
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