Answer:
The correct option is: When the amount of acid and base are equal
Step-by-step explanation:
Titration is an analytic method that is used to determine the concentration of an unknown solution, called titrand.
In this method, standard solution of known concentration, called titrant, is taken in the burette and added drop-wise to the titrand solution in the flask, until the endpoint is reached.
In case of an acid-base titration, a pH indicator is used, which changes the color of the solution when the endpoint is reached.
The endpoint indicates the equivalence point of an acid-base titration, where the concentration of the acid and base is equal.
Therefore, the correct option is: When the amount of acid and base are equal