In the third paragraph, the author discusses the role of asteroid strikes in mass extinctions primarily to undermine the value of expert judgments offered by paleontologists undermine the value of expert judgments offered by paleontologists A challenge a generalization made by certain astronomers challenge a generalization made by certain astronomers B suggest that volcanic eruptions are more destructive than asteroid strikes suggest that volcanic eruptions are more destructive than asteroid strikes C explain why volcanic eruptions are more common than asteroid strikes explain why volcanic eruptions are more common than asteroid strikes D acknowledge the merits of a position that he rejects