請依下文回答第 46 題至第 50 題 The United States doesn’t have one police force. Instead, there are different police agencies around the country. At the head of each police department is the Chief. The police force includes police officers and detectives. Police officers wear uniforms, and they respond to calls for help, direct traffic, investigate a burglary, etc. They often patrol a specific area and work with a partner. Detectives are plainclothes investigators who gather facts about specific cases. An officer or detective can be promoted to corporal, sergeant, lieutenant, or captain. Citizens who are at least 20 years old can enter the police force but there are specific requirements. They must pass certain written and physical examinations. In addition, senior officers, psychiatrists, or psychologists find out about the candidates’ personality by interviewing them or giving them a personality test.