What are the two main types of underground systems?

The correct answer identifies two main types of underground systems, specifically "Duct and Vault, and Direct Bury." These terms refer to widely adopted methods for installing and managing networks of utilities such as electrical, telecommunications, and water lines underground.

"Duct and Vault" systems involve installing utility lines within protective ducts or conduits, which are then housed in secure vaults. This method provides easy access for maintenance and repairs, reducing disruption to surface operations while protecting utilities from environmental elements.

"Direct Bury" refers to utilities installed directly in the ground without additional protective structures. This more straightforward approach can be cost-effective for certain applications but requires careful consideration regarding depth, soil conditions, and potential environmental hazards that may affect the buried materials.

The other answer choices do not accurately represent the primary types of underground systems. While terms like Trenchless, Open Cut, and Microtunneling pertain to methods of installation, they do not categorize the established formats of utility management as effectively as Duct and Vault, and Direct Bury. Therefore, selecting "Duct and Vault, and Direct Bury" captures the core approaches used in underground utility systems.