AB Hernandez is a transgender athlete. She won gold medals in jumping at a school sports event in California. Some people were happy, but some people were angry. Hernandez could play because of a new rule. Some people protested. They do not want transgender athletes in girls' sports. A sports group in California made the new rule because of Hernandez and a law. But some people think the new rule is not good. A recent study showed that many adults in the US do not think transgender female athletes should play in girls' sports.