根据句意,从方框中选择恰当的单词填空,每个限用一次,有的需要变换形式。 true, when, while, shock, hear 1. When I ________ the news, I was surprised. 2. ________ I was watching TV, my father came back home. 3. What were you doing ________ it started to rain? 4. Tell me the ________, or I will be angry with you. 5. Everyone was ________ to see the accident. 答案:1. heard 2. While 3. when 4. truth 5. shocked在一次数学活动课上,老师带领学生去测一条南北流向的河宽,如图所示,某学生在河东岸点A处观测到河对岸水边有一点C,测得C在A北偏西31°的方向上,沿河岸向北前行20米到达B处,测得C在B北偏西45°的方向上,请你根据以上数据,帮助该同学计算出这条河的宽度.(参考数值:tan31°≈,sin31°≈)