NEC ECC: Where in option C can I establish who holds responsibility for the design? (I.e D&B or Traditional)

We’re about to enter into a Option C contract as the main Contractor. The client is providing all the design. Where in the NEC contract is this made completely clear?

The clause 21.1 of both NEC3 and NEC4 ECC makes it absolutely clear that it has to be clearly stated in the Works Information/Scope what elements of the design Contractor is to do.

This would be further reinforced by whether clause X15 has been specified: if it has not, then the Employer clearly does not intend you to do design.