题目

In 1999, twelve percent of public elementary schools in the United States required students to wear uniforms. Just three years later, the amount was almost double that. A study of six big-city Ohio public schools showed students who were required to wear uniforms had improved graduation, behavior and attendance rates. Academic performance was unchanged. Some high schools in Texas have also joined in the movement. Yet studies find mixed results from requiring uniforms. And some schools have turned away from such policies. Supporters believe dressing the same creates a better learning environmen2．D～E时段，太阳直射点的移动方向是（　　）A．一直向北B．一直向南C．先向南后向北D．先向北后向南