The correct answer is C) to prevent cargo from coming in contact with the vessel's frames or shell plating. Cargo battens are installed in the cargo holds to create a space between the cargo and the vessel's structural members (frames) and shell plating (hull). This space prevents the cargo from directly contacting the vessel's structure, which could potentially damage the cargo or the vessel itself. By providing this separation, the cargo battens protect the cargo and the vessel's integrity. The other options are incorrect because they do not accurately describe the primary purpose of cargo battens. Option A is about securing a snatch block, which is not the function of cargo battens. Option B refers to supporting dunnage floors, which is a separate purpose. Option D is about providing fittings for cargo lashings, which is a secondary function of cargo battens, not the main purpose.