Here's why:

* Strong acids completely ionize in solution, meaning they donate all of their hydrogen ions (H+) to the solution.

* Hydrochloric acid (HCl) is a strong acid because it readily dissociates in water, forming hydrogen ions (H+) and chloride ions (Cl-):

```

HCl(aq) → H+(aq) + Cl-(aq)

```

* Concentration refers to the amount of acid dissolved in a given volume of solution. While concentrated hydrochloric acid has a high concentration of HCl, it's still a strong acid because it ionizes completely.

Important Note: Concentrated hydrochloric acid is extremely corrosive and dangerous. Always handle it with extreme care and follow proper safety procedures.