In United States v. Leon, what rule(s) was/were established?

In United States v. Leon, what rule(s) was/were established?
 
  A) good faith exception B) inevitable discovery
  C) poisoned tree doctrine D) poisoned tree doctrine and inevitable discovery

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(Question #2) Historically, ________ was/were developed in an effort to constrain kings and rulers who regarded themselves as above the law.
 
  A) rule of thumb B) discretion
  C) rule of law D) both discretion and rule of thumb

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(Question #3) Evidence of criminal activity can be seized if it is immediately apparent or in ________.
 
  A) plain view B) open field C) wingspan D) none of the above