To Maximize Profit,a Firm Hires Labour Until

To maximize profit,a firm hires labour until

A) there is no more labour available at the market wage rate.
B) they can sell that labour for no more than what they paid for it.
C) the wage rate paid to the labour equals the marginal cost of production.
D) the additional benefit of hiring the labour is equal to the additional revenue the labour generates.
E) the value of marginal product equals the wage rate.