Answer:
option (e)= 15 seconds.
Step-by-step explanation:
Titration is a chemical analysis used in the determination of the concentration of an identified analyte. To titrate, a known solution called the titrant is poured into the burette and then released stepwisely into an unknown solution until we have the END POINT.
END POINT marks the end of the titration. End point can be observe through colour change(here, we make use of indicators) , determining the Conductance and so on.
Quck note: Although option (e) = 15 seconds is the most correct option from the question, in reality titration is complete when the color change of the indicator retains it color for MORE THAN 15 SECONDS.
Apparatus needed for titration: pipette, burette, measuring cylinder, and beakers.