Introduction:
When the scope of the construction work is well-defined with all its drawings, specifications, quantities, and estimates, choosing the most suitable contract type becomes crucial. The preferred contract should provide clarity, reduce risk, and ensure that the project is completed within the defined scope and budget.

Explanation:
Among the given options, the most preferred contract type in this scenario is the Lump sum contract (option D). This can be justified by considering the following factors:

1. Fixed Price:
- A lump sum contract is a fixed price contract where the contractor agrees to complete the project for a specific sum of money.
- With a well-defined scope, drawings, specifications, and quantities, a lump sum contract allows the project owner to accurately determine the total cost of the project upfront.
- This provides financial stability and predictability, as the contractor is responsible for any cost overruns or additional expenses that may arise during the construction process.

2. Clarity and Simplicity:
- A lump sum contract provides a clear and straightforward agreement between the project owner and the contractor.
- The scope of work, deliverables, and timelines are clearly defined in the contract, minimizing the potential for disputes or misunderstandings.
- This simplicity makes it easier for both parties to manage and monitor the progress of the project.

3. Risk Allocation:
- With a lump sum contract, the risk is primarily borne by the contractor.
- The contractor is responsible for completing the project within the agreed-upon budget, regardless of any cost fluctuations or unforeseen circumstances.
- This allows the project owner to transfer a significant portion of the risk to the contractor, providing a higher level of financial security.

4. Cost Control:
- A lump sum contract promotes cost control and cost certainty.
- Since the scope of work and quantities are well-defined, the contractor is incentivized to carefully plan and manage the project to avoid any cost overruns.
- This ensures that the project is completed within the allocated budget, providing financial benefits to the project owner.

Conclusion:
Considering the well-defined scope of work, drawings, specifications, quantities, and estimates, a lump sum contract is the most preferred contract type. It offers fixed pricing, clarity, simplicity, effective risk allocation, and cost control. However, it is essential to carefully draft and negotiate the contract terms to ensure that all project requirements are adequately addressed.