In universal indicators, a pH of 4 to 5 indicates-

Correct option is B

The correct answer is (b) Weak acids.
· pH Scale: The pH scale ranges from 0 to 14, with 7 being neutral. Values below 7 indicate acidity, while values above 7 indicate alkalinity (basicity). The further away from 7, the stronger the acid or alkali.
· Weak Acids: A pH range of 4 to 5 falls within the acidic side of the pH scale but closer to neutral (7) than to very acidic (0-3). This range indicates a weak acid. Weak acids do not completely dissociate in water and thus have a higher pH than strong acids.
· Universal Indicator: A universal indicator is a mixture of several indicators that provides a color change across a wide range of pH levels, making it possible to determine the acidity or alkalinity of a solution more accurately. For pH values of 4 to 5, the universal indicator typically shows an orange to yellow color, indicating a weak acidic nature.
Additional details on other options:
· Strong alkalis: These have pH values typically between 11 and 14.
· Weak alkalis: These have pH values typically between 8 and 10.
· Strong acids: These have pH values typically between 0 and 3.