The correct answer is B) The applicable gross and net tonnage of the ship will change if this mark is submerged and the load line mark is visible. This is the correct answer because the symbol shown in illustration D022DG represents the Plimsoll mark, which indicates the maximum safe draft or load line of a vessel. If the Plimsoll mark is submerged and the actual load line mark becomes visible, it means the vessel is overloaded, which will affect its gross and net tonnage measurements. The other answer choices are incorrect because: A) The Plimsoll mark is not specific to Great Lakes voyages, C) The Plimsoll mark is used on all commercial vessels, not just government vessels, and D) The line under the triangle is not the summer load line, but rather the Plimsoll mark itself.