Which of these sentences is correctly written and punctuated? Keeping his active mind challenging Roosevelt improved his stamp collection, and read books on American history, politics, and biography. To keep his active mind challenging, Roosevelt improved his stamp collection, reading books on American history politics and biography. Keeping his active mind challenged Roosevelt improved his stamp collection reading books on American history, politics, and biography. To keep his active mind challenged, Roosevelt improved his stamp collection and read books on American history, politics, and biography.