What options are available at bid time for items without complete information?

The correct choice indicates that allowances and unit prices are viable options at bid time for items lacking complete information. Allowances refer to a predetermined sum allocated for a specific part of the project where the final cost cannot be accurately determined at the time of bidding. This provides flexibility for the contractor to cover costs that are still uncertain.

Unit prices, on the other hand, establish a set price per unit of measure for materials or work that might be required in varying quantities. This mechanism allows for adjustments in the contract amount based on actual quantities encountered in the field, ensuring that the contractor can still operate within a framework without needing comprehensive details at the outset.

Considering the other choices, while they may include combinations of these two elements, only the option that combines allowances and unit prices directly addresses the needs for managing uncertainties at bid time. The inclusion of alternates – which typically provide options to add or substitute specific parts of the work – is not necessary where allowance and unit price strategies adequately cover uncertainties.