What occurs if an Equipment or Fortification is attached to an illegal permanent?

When an Equipment or Fortification is attached to a permanent that becomes illegal to be attached to, the correct outcome is that the attachment goes away, but the Equipment or Fortification itself remains on the battlefield. This is based on the comprehensive rules governing attachments.

According to the rules, if a permanent on which an Equipment or Fortification is attached becomes illegal for that attachment (such as if the creature it was equipped to dies or the land it was fortified is destroyed), then the Equipment or Fortification simply becomes unattached. It does not leave the battlefield or return to the owner's hand but continues to exist where it is.

The other options create incorrect scenarios regarding what happens to the Equipment or Fortification when its attachment becomes illegal. Returning it to the owner's hand or sending it to the graveyard would not happen in this situation, as it remains in play but simply loses the attachment. Similarly, the Equipment or Fortification does not undergo any activation state by being attached or unattached; that aspect pertains mainly to its abilities and the timing of such activations.