Answer:
insert()
Explanation:
StringBuilder is a dynamic object which is used to create the string without any size restriction.
let discuss the option:
option a: append()
It is a function which is used to append the two string. but it not add the character at specific location.
option b: charAt()
it is function which is used to get the character at specific location.
option c: insert()
It is a function which is used to add the character at specific location, it takes two parameter location and character.
option d: setCharAt()
it is a function which is use to update the character at specific location.
Therefore, the correct option is c.
