Choice "B" is correct. If a director acts in good faith and in a manner the director believes is in the best interest of the corporation, and the director exercises the care that a reasonably prudent person would exercise in a similar position, the director is protected against liability for decisions the director makes that turn out poorly for the corporation. This is commonly known as the business judgment rule.
Choice "d" is incorrect. The clean hands doctrine (better known as the unclean hands doctrine) is a defense in actions brought in cases seeking equitable relief (e.g., an action seeking specific performance of a contract). If a person seeking equitable relief has acted improperly in the transaction before the court, he is said to have unclean hands and the court will not grant equitable relief. The doctrine has nothing to do with releasing directors from liability for acting in good faith and is outside the scope of the CPA Exam topics.
Choices "c" and "a" are incorrect. There are no such rules. Full disclosure may be required in certain situations under corporate law, but such disclosure requirement is not the described doctrine.