Which statement about acids is the most correct?

Correct answer: All acids tend to give hydrogen ions in water

The governing concept is the aqueous definition of an acid. In water, an acid increases the concentration of hydrogen ions, more accurately forming hydronium ions, H₃O⁺. This explains acidic behaviour and indicator changes. Acids are not all safe; some are corrosive. Acids turn blue litmus red, not red litmus blue. Option D is also incorrect because acids are substances, not necessarily metals. Thus option A gives the scientifically correct general statement.