For every kid who really wants to know--and for every exasperated parent who simply doesn't know--here is a lively omnium-gatherum of explanations to the most frequently asked questions about our world, from "Why do stars twinkle?" to "What are hiccups? "Taken from Kathy Wollard's popular column, "How Come?" (seen for the past six years in "Newsday" and recently syndicated nationally through the "Los Angeles Times"), "How Come?" explains why cats...