Answer:
lagoon
Explanation:
As the estuary gets more and more sediments, the deposition of them is constantly on the rise, affecting the landscape and forming new geographical features. With the sediments constantly building up, they eventually cut off part of the water from the sea. They will form a closed pool-like feature, filled with water, and surrounded by sediments, cut off from the sea. It will have shallow water, and because the water is stagnant and shallow it will have higher temperature than the other water. This geographical feature is known as lagoon.
Answer: Classified as a theory.
Explanation: The dictionary definition of theory is a system of ideas that are used to logically explain something. It also says that they are also based off of something not entirely connected to the thing the theory is being made about.
Because the idea that the universe has expanded explains such a large number of observations, which in turn leads to more predictions and therefore more observations that support it, this becomes your system of ideas. Because this system was based off of the aforementioned observations in the first paragraph, this proves that it is best classified as a theory.