Synthetic indicator among the following is:

Correct option is D

The correct answer is Phenolphthalein.
Synthetic indicators
· Synthetic indicators are acid-base indicators made from artificial substances.
· They are created in laboratories.
· Examples of Synthetic indicators:
· Phenolphthalein:
· Phenolphthalein is a synthetic indicator that is colourless in acidic solutions but pink in basic solutions.
· It is most commonly used in acid-base titrations.
· Methyl orange:
· In acidic medium, methyl orange appears red; in basic medium, it appears yellow.
Additional Information
Natural indicators
· The acid-base indicators obtained from natural sources are known as natural indicators.
· Examples of Natural indicators:
· Litmus:
· Litmus is the most widely used natural indicator.
· It is derived from lichens.
· It has a mauve (purple) colour in distilled water. When added to an acidic solution, it turns red and when added to a basic solution, it turns blue.
· It is available as a solution or in the form of strips of paper known as litmus paper.
· It is typically available in red and blue litmus paper.
· Turmeric:
· The colour of turmeric does not change in acidic medium, but it changes from yellow to deep red in basic medium.
· China rose petals (Gudhal):
· China rose indicator turns acidic solutions to dark pink (magenta) and basic solutions to green.