question: What sentence would provide a factual answer to this question: "If a glacier going past a dock brushed up against some large boulders there, the stones would"

answer: glaciers cause scratches in rocks

question: What sentence would provide a factual answer to this question: "An electrical conductor is needed to"

answer: An electrical conductor is a vehicle for the flow of electricity

question: What sentence would provide a factual answer to this question: "Which is the likeliest part of a pencil to have been mined?"

answer:
pencil lead contains mineral graphite