Which of the following statements are true? Select one correct answer:

a.

If unemployment benefits decrease, the minimum cost of a unit of effort for the employer will rise.

b.

If an employee's disutility of effort increases, the reservation wage will rise.

c.

If the wage doesn't change, employees will work harder in periods of high unemployment.

d.

If workers continue to receive benefits however long they remained unemployed, an increase in the level of unemployment will have no effect on the best response curve.