The key issue in this question is the allocation of design responsibility and the treatment of unforeseeable physical conditions (particularly relevant for underground works or inaccessible areas).
The Yellow Book 2017 is specifically designed for projects where the Contractor is responsible for both design and execution, while still maintaining a balanced risk allocation. Importantly, Sub-Clause 4.12 [Unforeseeable Physical Conditions] allows the Contractor to claim additional time and/or cost for conditions that could not reasonably have been foreseen. Therefore, for projects involving underground or uninspectable works, the Yellow Book is highly appropriate. Hence, Option A is correct.
The Silver Book 2017 (EPC/Turnkey) also places full responsibility for design and execution on the Contractor. However, it adopts a much stricter risk allocation: the Contractor generally bears the risk of unforeseen physical conditions. This makes it less suitable for projects with significant uncertainty—unless amendments are made. By modifying Sub-Clause 4.12 in the Particular Conditions to reallocate risk (e.g., allowing relief for unforeseeable conditions), the Silver Book can be adapted for such projects. Therefore, Option C is correct.
Option B (Red Book) is incorrect because design responsibility primarily lies with the Employer, not the Contractor.
Option D is incorrect because using the Silver Book without amendment would place excessive and potentially unmanageable risk on the Contractor in cases involving unknown subsurface conditions.
This reflects a core FIDIC principle: selecting the appropriate form depends heavily on risk allocation and the degree of uncertainty in site conditions.
