Question: What is the question to: "Approximately 72% of the planet's surface (~3.6x108 km2) is covered by saline water that is customarily divided into several principal oceans and smaller seas, with the ocean covering approximately 71% of the Earth's surface."? The topic is Ocean.
Answer: "how much of earth is covered ocean water?"

Question: What is the question to: "A gristmill (also: grist mill, corn mill or flour mill) grinds grain into flour ."? The topic is Gristmill.
Answer: "what is grist mill stone?"

Question: What is the question to: "LSD is non-addictive, is not known to cause brain damage, and has extremely low toxicity relative to dose ."? The topic is Lysergic acid diethylamide.
Answer:
"how does lsd impact the human body?"