The concerted action requirement of the Sherman Act Section 1:

A) may be established by an express agreement.
B) is not met when a parent corporation and its wholly owned subsidiaries agree to a restraint in trade.
C) requires factors, additional to conscious parallelism, such as identical sealed bids from each competitor.
D) All of these are true.

Concerted Action Requirement

A legal criterion necessitating a cooperative or joint effort among individuals or entities to achieve a particular outcome.

Conscious Parallelism

A situation where firms in an industry independently choose similar pricing, production, or marketing practices without explicit agreement.

Wholly Owned Subsidiaries

Companies fully controlled by another company, the parent company, because the parent company owns 100% of the subsidiary's shares.