question: What sentence would provide a factual answer to this question: "Which is true?"

answer: the composition of something can be used to identify that something

question: What sentence would provide a factual answer to this question: "A thermometer would be used to"

answer: a thermometer is used to measure temperature

question: What sentence would provide a factual answer to this question: "If a person looks at the night sky in February and then again in June, the stars will be"

answer:
the Earth revolving around the sun causes stars to appear in different areas in the sky at different times of year