question: What sentence would provide a factual answer to this question: "Digestion is when stomach acid breaks down what?"

answer: digestion is when stomach acid breaks down food

question: What sentence would provide a factual answer to this question: "In a warm room, it is likely that the source of heat is"

answer: a radiator is a source of heat

question: What sentence would provide a factual answer to this question: "Grooves in the ground are a sign of"

answer:
soil loss causes grooves in soil