What are two differences between a notice and other communications under the FIDIC Red Book...

Option A is correct: “Notice” is a defined term under FIDIC 2017 Red Book; “Other Communications” is a separate category, also defined but distinct.

Option D is correct: Notices, Notices of Dissatisfaction, and Certificates require delivery to all Parties and the Engineer, whereas other communications may not have such strict requirements.

Option B is incorrect as there are contractual differences.

Option C is partially correct but “Other Communications” and “Notice” are distinct terms, so A is more precise.