“The symbol H stands for ___ of hydrogen.A.One atomB.One moleculeC.One ionD.Two atoms

The symbol \( \text{H} \) stands for **one atom** of hydrogen.

Here's an explanation:

- **One atom**: The symbol \( \text{H} \) represents a single hydrogen atom. In chemical notation, elements are often represented by their chemical symbols, which indicate the basic unit of the element in question. For hydrogen, the symbol is \( \text{H} \), representing one atom of hydrogen.

- **One molecule**: A molecule of hydrogen gas is represented by \( \text{H}_2 \), which indicates two hydrogen atoms bonded together.

- **One ion**: A hydrogen ion is usually represented as \( \text{H}^+ \) (a proton) or \( \text{H}^- \) (a hydride ion), but the symbol \( \text{H} \) itself does not indicate an ion.

- **Two atoms**: This would be represented as \( \text{H}_2 \), not \( \text{H} \).

So the correct answer is **A. One atom**.