Which one of the following is a good example of ‘scaffolding

Which one of the following is a good example of ‘scaffolding (learning of a problem solving task till the student is able to do it by herself)?
(a) Offering a reward for solving the problem quickly
(b) Telling her that she can do it by trying again and again
(c) Providing a half-solved example
(d) Telling her she cannot go home till she solves the problem