Select the correct answer regarding tacit collusion

Group of answer choices

a. Companies can communicate formally and explicitly or informally in secretive ways so long as there is a formal but secretive arrangement between them explicitly articulated, which would not be considered collusion at all.

b. Companies meet outside an alliance in person to set up an explicit confidential strategy to align prices and beat the rest of the competitors.

c. Companies with no alliances communicate with one another in subtle, informal confidential ways to collude with one another on prices without explicitly speaking with one another, which would not be considered tacit collusion.

d. Companies within an alliance can communicate with one another in subtle, secretive, and legal ways, and it would not be considered tacit collusion.