题目

Liu Xu is a student from a middle school in Guangxi. Once he was riding home when a  robber (盗贼) suddenly jumped out from the roadside. He pulled Liu Xu off his bike and rode away. Liu Xu was scared, but he didn’t run after the robber. He found a telephone and called the police at 110.“Safety is the first important in such a situation,” Liu said, remembering what his teacher had told him in his first aid class. “It is not safe to run after an adult who is stronger than you.” Liu’s school has compulsory (必修的) first aid education. Students must take the class once a week. -的绝对值是（ ）A．-2B．-C．2D．