An increase in a perfectly competitive firm's demand for labor could be caused by an increase in the amount of human capital among the labor force.

a. a decrease in the market price of the product the firm produces.
b. an increase in the supply of labor.
c. a decrease in the market wage rate.

c.a decrease in the market wage rate.

Explanation:

A perfect competition is characterised by many buyers and sellers of homogenous goods and services. Market prices are set by the forces of demand and supply. There are no barriers to entry or exit of firms into the industry.

In the long run, firms earn zero economic profit. If in the short run firms are earning economic profit, in the long run firms would enter into the industry. This would drive economic profit to zero.

Also, if in the short run, firms are earning economic loss, in the long run, firms would exit the industry until economic profit falls to zero.

If wage rate of labour falls, it means labour becomes cheaper to employ. This would lead to an increase in the demand for Labour.

If demand for a good falls, firms would cut down on production and would reduce demand for Labour

If supply of labour increases, it doesn't mean that the demand for Labour has to increases

I hope my answer helps you

explanation: doctrine of respondeat superior is a legal doctrine that is commonly used in tort. this principle makes an employer or principal legally responsible for the wrongful acts done by an employee or agent, if such acts occur within the scope of the employment or agency.