Confusion in the Ranks

• WWizards of the Coast2004-10-04
  Official Ruling
  The exchange isn't optional. If there is a legal choice, you must make one.
• WWizards of the Coast2004-12-01
  Official Ruling
  Confusion in the Ranks triggers on itself entering. If an opponent controls an enchantment, exchange Confusion in the Ranks for that enchantment.
• WWizards of the Coast2004-12-01
  Official Ruling
  The permanents are exchanged only if they're both on the battlefield when the ability resolves.
• WWizards of the Coast2004-12-01
  Official Ruling
  The permanents have to share a permanent type both when the target is chosen and when the ability resolves.
• WWizards of the Coast2004-12-01
  Official Ruling
  Even though Confusion in the Ranks triggers only when an artifact, creature, or enchantment enters, the ability can target a land if the permanent entering is an artifact land.

Rulings via Scryfall