Final answer:
In property law, Tanya's acquisition of land through natural river deposits is known as accretion, which is the gradual increase of land by natural causes. Option 4 is correct.
Step-by-step explanation:
The concept of acquiring ownership of land through natural processes like the deposit of soil by water sources is a topic relevant to law, specifically property law. In the scenario presented, homeowner Tanya acquires the ownership of land that was deposited by a river flowing through her property.
The correct term for this process is accretion. Accretion is the gradual and imperceptible deposit of earth materials by natural causes, which results in the increase of land area.
It's distinct from other terms like reliction, which refers to the increase of land area when water recedes naturally; avulsion, which describes a sudden and perceptible change where land is either lost or gained; and succession, which in another context refers to the order of inheritance or to ecological processes where species in a community change over time.
Hence, option 4 is correct.