Severance is the physical or legal act of removing an item from the real estate so that it becomes personal property. Therefore C is correct. A common example is a tree growing in the ground: while rooted to the land, it is ordinarily part of the real property. Once cut down and separated from the soil, the resulting timber generally becomes personal property.
Annexation describes essentially the reverse process. Personal property can become a fixture—and therefore part of the real estate—when it is attached with sufficient permanence and with circumstances showing an intent that it remain. The precise fixture analysis can involve the method of attachment, adaptation to the property, relationship of the parties, and intention.
Hypothecation concerns pledging property as security while retaining possession; it does not convert realty into personalty. A fiduciary relationship concerns duties of trust and loyalty and has nothing to do with the physical classification of property.
The real-property/personal-property distinction is important in sales contracts because parties should make clear whether movable items are included, excluded, or separately conveyed.
Study Guide Reference: Property Ownership — real versus personal property; fixtures, annexation and severance.
