Introduction to Sharks and Rays: Which sharks are dangerous to humans? How do sharks find food? What happens when sharks are in a state of bloody violence? What animal was the ancestor of sharks? Can rays become friends with humans? How big is the biggest ray? Weitus Pi Delouscher, a famous popular science writer, explained the amazing abilities and sensory organs of sharks to readers, and introduced the rays, a close relative of sharks. He enthusiastically analyzed the mysterious behavior of sharks and corrected people's prejudice against sharks. He successfully showed people these two fascinating animals with gripping stories and carefully selected pictures, which are still rarely understood by people.