Generate a sentence that answers this question: "A thing is on fire and afterwards it is".

Answer: fire causes burning

Generate a sentence that answers this question: "a student leaves a nail line on a mineral sample, so that mineral can be described as what?".

Answer: if a mineral can be scratched by a fingernail then that mineral is soft

Generate a sentence that answers this question: "Viruses are killed by objects used in a".

Answer:
adding heat to something kills viruses in that something