The marginal productivity theory states that if a firm operates in a perfectly competitive factor market, it pays each factor of production its marginal revenue product. However, this theory may fail to hold if factor markets are not competitive.
One circumstance under which factor markets may fail to be competitive is if there is imperfect information.
Which of the following are ways in which firms seek to overcome information problems? Select all that apply.

a) Only hiring workers who have earned good grades in college.
b) Always hiring from the outside to avoid being accused of discrimination.
c) Promoting workers from within the company who have shown themselves to be productive, rather than hiring from outside.

A perfectly competitive factor market can be defined as a perfectly competitive market where all the products produced by different manufacturers are the same, the product cost and the price of the product are known to all parties etc.

Imperfect information in economics refers to a situation where the information among different parties such as manufacturer, consumer etc is not equal and balanced.

The correct answer among the given options is A, hiring workers that have earned good grades in college to make up for the information imbalance and overcome the imperfect information problem.

I hope this answer helps.