题目

 They are also asking parents to keep a close watch on their children, especially during ______ they call the risky period: between the middle of the day and sunset. A. what        B. which     C. that       D. when 答案：A（2006?扬州模拟）南北半球昼夜等长时，太阳直射在（　　）A．赤道B．北回归线C．南回归线D．赤道与回归线之间的某一点