The correct answer is D) All of the above. This is because the Inland Navigation Rules specify that the presence of a partly submerged object being towed must be indicated by an all-round light at each end of the towed object, a diamond shape on the towed object, and a searchlight beamed from the towing vessel in the direction of the tow. All three of these visual signals are required to properly mark the presence of a submerged object being towed, so option D covering all of these requirements is the correct answer. The other options are incorrect because they do not fully meet the Inland Navigation Rules for marking a towed, partly submerged object. Options A, B, and C each describe only one of the required visual signals, rather than the complete set of markings needed.