Which dwelling form offers open peril coverage on the building?

The DP-3 (Special) dwelling form offers open peril coverage on the building, which means it provides coverage for risks unless specifically excluded in the policy. This is broader than other forms, as it covers all perils that are not explicitly listed as exceptions.

In contrast, the DP-1 (Basic) dwelling form provides coverage on a named peril basis, which means it only covers specific perils that are listed in the policy. This limits the coverage significantly compared to open peril policies. The DP-2 (Broad) form also has named perils but includes more coverage than the DP-1; however, it still does not provide the comprehensive protection of the DP-3. The DP-4 (Comprehensive) form is a less commonly used dwelling form that is typically for mobile homes and may not apply directly in the same context as the others mentioned.

Therefore, the DP-3 is the only form that provides the most extensive coverage through its open peril approach for building protection, making it the correct choice among the options listed.