Li[y所在班级准备后天去沙湖公园野餐。今天下午，她去Mike家通知他参加活动，但他不在．请你以Lily的身份给他留言，主要内容：早上7:30在校门外集合，骑自行车去，自带2个面包和3瓶桔子汁作食物：穿运动鞋，若下雨，活动改在下周六。

A．to show that we are good at using them
B．to show that we are polite
C．to prove that we are not silly
D．to express exactly what we mean

A. ways to develop economy
B. systems of rewarding students
C. approaches to solving problems
D. methods of improving performance