How far should cyclists ride from parked cars to avoid the "door zone" and reduce the risk of getting hit by opening vehicle doors?

• At least two feet from parked cars
• At least three feet from parked cars
  Explanation:

  "Bicyclists should ride at least three feet from parked cars to avoid doors on streets with and without bike lanes. This will keep bicyclists outside the "door zone" and protect them from getting hit by opening vehicle doors."
• At least four feet from parked cars
• At least five feet from parked cars