The correct answer is B) leave it to port when southbound on the Atlantic portions of the ICW. The reason this is the correct answer is that a dayboard with the designation "TR-SY" indicates a preferred channel dayboard, which means the vessel should pass the dayboard to the preferred or "safe" side, which in this case is to port when traveling southbound on the Atlantic portions of the Intracoastal Waterway (ICW). The other answer choices are incorrect because A) is looking for the wrong type of dayboard, C) is not the correct action for a preferred channel dayboard, and D) is incorrect as a preferred channel dayboard does have lateral significance.