A significant advantage of a multi-hull boat is:

A significant advantage of a multi-hull boat is the wider space it provides when turning. Multi-hull boats, such as catamarans and trimarans, have more stability and a greater beam compared to single-hull boats. This wider beam allows them to maintain stability while making turns, reducing the risk of capsizing and providing a more comfortable and controlled turning experience. The increased surface area and buoyancy of the hulls help in turning more smoothly compared to traditional monohulls, which can be prone to leaning and potentially tipping during sharp maneuvers.

While other options may seem appealing, they do not accurately describe the primary advantages offered by multi-hull boats. For instance, better fuel efficiency can vary depending on the design and intended use of the boat. The ability to navigate shallow waters is also not a defining characteristic of multi-hulls; typically, they might require deeper water because of their wider beams and keels. Reduced construction cost is not generally associated with multi-hull boats as they can be more complex and expensive to build compared to monohulls.