In the context of registered land, the most effective way to protect an option agreement is to register it as a notice on the title of the property. A notice is an entry made in the register to protect an interest affecting a registered estate or charge. This ensures that any potential purchasers or interested parties are aware of the option agreement, thereby protecting the property developer’s interest in the property. Registration as a land charge is applicable to unregistered land, and options cannot be registered as overriding interests or registrable dispositions. Therefore, the correct method for protecting the option in this scenario is by registering it as a notice. 

Key Point: This question emphasizes the importance of understanding the methods available for protecting interests in registered land. Registering an option agreement as a notice ensures the interest is protected and known to third parties dealing with the property.