题目

    Exercise is the best way to stay healthy. But few people get enough exercise. Only 20% of Americans get 150 minutes of physical activity every week. More than 80 million Americans over 6 years old are not active (活跃的). Many US schools cut (削减) PE classes. Only 15% of schools have this class at least three days a week. This year, the US National Institutes of Health (NIH) starts an important study. It will show the things happening inside a body after exercise. The NIH hopes to tell people that exercise is a kind of good medicine. The study will run for six years. It stud①点A位于（9，2）处．从A点先向北走4cm到点B，点B位置是　 　；再向东走6cm到达点C，点C位置是　 　．连接点A、B、C，那么三角形ABC是　 　三角形．②将三角形ABC绕点A按逆时针旋转90°，画出旋转后的图形．此时点B运动了　 　cm．③把三角形ABC各边缩小到原来的，画出缩小后的图形，它的面积是　 　cm2．④点D在A点南偏东80°方向的5cm处，标出点D，要有画图过程．