The correct answer is D) Emergency shutdown. When the HI-HI liquid level set point is reached while loading an LNG (Liquefied Natural Gas) tank, an emergency shutdown (ESD) system will be activated. This is a critical safety feature required by regulations to prevent an overflow and potential hazardous situation. The ESD system will automatically shut down the loading process and close the appropriate valves to isolate the tank and stop the flow of LNG. The other options are incorrect because they do not adequately address the critical safety requirement to initiate an emergency shutdown in this scenario.