Answer:
The correct answer is the option C: an agreement among firms to charge the same price or otherwise not to compete.
Step-by-step explanation:
To begin with, the name of "collusion" refers to an economy concept that focus on the situation where two or more companies decide to work together ilegally by taking a same strategy such as pricing the goods with a same amount so in that order the limit or at least intent to restrict the competion so in that way those firms can keep a piece of the market for themselves. It is consider ilegally in the countries because it is an disadvantage for the competition.