When silver articles react with a particular substance, they turn black. The correct answer is option 1: sulphur. Silver reacts with sulphur in the air or in items such as eggs, onions, or rubber to form a compound called silver sulphide. This compound is black in color and causes the silver articles to appear black.

Option 2: oxygen is incorrect because silver does not react with oxygen alone in the air to form a black compound. Instead, it forms a thin layer of silver oxide, which does not cause the black color.

Option 3: carbon dioxide is also incorrect because silver does not react with carbon dioxide in the air to form a black compound.

Option 4: phosphorus is incorrect because silver does not react with phosphorus to turn black. Phosphorus can react with other substances to form compounds, but it does not cause silver articles to turn black.

In summary, the correct substance that makes silver articles black is sulphur.