The correct answer is (d). Both the degree or mode of annexation and the object of annexation are factors that determine whether something attached to the earth is to be regarded as immovable or not.
The degree or mode of annexation refers to how firmly something is attached to the earth. For example, a tree that is firmly rooted in the ground is considered to be immovable, while a tree that is only loosely planted in a pot is considered to be movable.
The object of annexation refers to the purpose for which something is attached to the earth. For example, a fence that is built to enclose a property is considered to be immovable, while a fence that is built to protect a garden from animals is considered to be movable.
In some cases, the degree or mode of annexation may be more important than the object of annexation. For example, a statue that is firmly attached to a pedestal is considered to be immovable, even if the statue is not intended to be permanent. In other cases, the object of annexation may be more important than the degree or mode of annexation. For example, a tent that is pitched on a campsite is considered to be movable, even if the tent is firmly attached to the ground.
Ultimately, the determination of whether something attached to the earth is to be regarded as immovable or not is a matter of law. In most jurisdictions, the law will specify the factors that are to be considered in making this determination.