ANS:C - three pipes

A design involving "three pipes" in the context of an inverted siphon is less common and typically not the standard configuration. However, it's conceivable that in some specific engineering scenarios or large-scale projects, designers may opt for a setup involving three pipes for an inverted siphon. Here's a theoretical explanation of how a system with three pipes might work:

1. Increased Capacity: One potential reason for using three pipes instead of one or two could be to increase the overall capacity of the inverted siphon system. By having three pipes running in parallel, the system can accommodate a higher volume of flow compared to a single or dual-pipe configuration.
2. Redundancy and Reliability: Having multiple pipes provides redundancy in the system. If one pipe becomes blocked or requires maintenance, the flow can be diverted to the remaining operational pipes, minimizing disruption to the overall flow within the system. This redundancy can enhance the reliability and resilience of the infrastructure.
3. Distribution of Flow: In certain situations where the flow rate varies significantly or unevenly, distributing the flow across multiple pipes can help ensure more uniform flow distribution and reduce the risk of surges or uneven pressure within the system.
4. Construction Constraints: The terrain or construction constraints may also influence the decision to use three pipes. For example, the available space or the layout of the surrounding infrastructure may necessitate a design with three pipes to accommodate the required flow capacity while conforming to site-specific constraints.

It's important to note that the design of inverted siphon systems, including the number of pipes used, depends on various factors such as hydraulic requirements, site conditions, budget constraints, and engineering considerations. While a three-pipe configuration may offer certain advantages in specific scenarios, it's not the typical or standard configuration for inverted siphon systems, which more commonly involve one or two pipes.