Red litmus paper serves as an indicator that changes color to blue in the presence of a basic (alkaline) solution. By definition, basic solutions have a pH value greater than 7. Therefore, any solution that turns red litmus blue must have a pH higher than 7.

A Universal Indicator is a mixture of several pH indicators that exhibits a wide range of color changes across the entire pH scale (0-14). Unlike simple indicators like litmus or phenolphthalein, which only show a binary color change at a specific transition point, the Universal Indicator allows for a more precise estimation of the pH value.

Blue litmus paper turns red in the presence of an acid. A base solution (2) will keep the paper blue, and a common salt solution (3) is neutral, meaning it will also not change the color of the litmus paper. Therefore, both 2 and 3 do not turn blue litmus red.

Acids are defined by their ability to neutralize bases to form salt and water. While option D is also a property of acids (as they are electrolytes), neutralization is a fundamental chemical characteristic. Option A describes a base, and option B describes an Arrhenius base. The question asks for a property on an acidic basis, and neutralization is the hallmark reaction.

The titration of sodium carbonate (a weak base) with sulfuric acid (a strong acid) involves the formation of carbonic acid. Phenolphthalein is often used to detect the first equivalence point in carbonate titrations. Note: Methyl orange is also frequently used for the second equivalence point, but phenolphthalein is a standard choice for specific stages of this titration.

A universal indicator changes color based on the pH of the solution. In acidic conditions, it shifts toward red or orange. In neutral conditions, it appears green. In basic or alkaline conditions, the indicator shifts toward blue or purple, depending on the concentration of hydroxide ions present in the solution.

Phenolphthalein is a pH indicator that remains colorless in acidic and neutral solutions but turns pink in basic (alkaline) solutions. Since solution 'B' is an alkali, it will cause the phenolphthalein to change color to pink.

Sodium chloride is a neutral salt formed by the reaction between hydrochloric acid (HCl), a strong acid, and sodium hydroxide (NaOH), a strong base. This neutralization reaction produces water and the salt NaCl, which does not undergo hydrolysis in water, resulting in a neutral pH.

Phenolphthalein is a pH indicator that turns colorless in acidic solutions and pink or magenta in basic (alkaline) solutions. Methyl orange is another indicator that appears red in acidic conditions and yellow in basic conditions. Thus, an alkali will turn phenolphthalein pink and methyl orange yellow.

Olfactory indicators are substances that change their characteristic smell when added to an acidic or basic solution. Examples include onion, vanilla extract, and clove oil. These are distinct from visual indicators that change color based on pH levels.