question: What sentence would provide a factual answer to this question: "A telescope is used to observe what?"

answer: a telescope is used for observing stars

question: What sentence would provide a factual answer to this question: "Which would likely result in a chemical change?"

answer: An example of a chemical change is acid breaking down substances

question: What sentence would provide a factual answer to this question: "What causes objects that have mass to be pulled down?"

answer:
gravitational force causes objects that have mass to be pulled down on a planet