Final answer:
The tunnel-like structure created by extending a round arch in depth is called a Barrel Vault, which is made up of a series of arches forming a tunnel shape and is supported by thick walls. Correct answer is C) Barrel Vault.
Step-by-step explanation:
When extended in depth, the round arch creates a tunnel-like structure called a Barrel Vault. This architectural feature consists of a line of arches placed in sequence to form a tunnel shape. It is the basic form of a vault and has been used in a variety of buildings, from Roman basilicas to Romanesque churches. The Barrel Vault is a single arched structure that supports the stone ceiling and is characterized by thick, massive walls that provide the necessary support to counteract the lateral thrust of the vault.
Barrel vaults consist of a line of arches in a row that create the shape of a tunnel. This architectural structure was commonly used in Roman buildings, such as basilicas and churches, to provide covered transport and connect different areas of the building. Therefore, the correct answer is C) Barrel Vault.