The correct answer is D) Veer out more chain on the port anchor. When an anchor begins to drag in an open roadstead, the first action you should take is to veer out more chain on the port anchor. This increases the scope (length) of the anchor rode, which helps the anchor dig in deeper and grip the seabed more securely. Putting the engines slow ahead or dropping the starboard anchor would not be the best initial response, as they may not be as effective as simply paying out more chain on the existing anchor. The other options could be considered if veering out more chain does not stop the anchor from dragging, but this should be the first step taken.