Four solutions of the same volume are tested with a conductivity meter. Which one conducts electricity best?

1. An electric current is a movement of charged particles. 2. In a solution the charge carriers are the mobile ions, so conductivity depends on how many ions are present. 3. Two separate things control that number, and both must be considered. 4. Strong means a large fraction of the acid molecules ionise, weak means only a small fraction do. 5. Concentrated means a lot of acid was added to the solvent, dilute means very little was added. 6. The most ions therefore come from an acid that is both strong and concentrated. 7. A concentrated weak acid is the trap for anyone who reads concentrated as meaning strong, since most of its molecules stay whole. 8. A dilute strong acid ionises fully but has few molecules to start with, and a dilute weak acid is the poorest conductor of the four. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 9: Acids and bases_