题目

   Food safety is a problem in all places around the world and people in different areas of the world prepare foods in different ways. The WHO released(发布)five simple rules for preparing food in a safe way. They call these rules the “Five Keys to Safer Food”. Key 1: Keep clean ____46   . People should wash their hands often — before touching food and while they are preparing food. People should wash all surfaces and equipment used for preparing food. Key 2: Separate raw (生的) and cooked Raw foods should not touch prepared foods.____47___ Key 3:   48    People sh（2003•上海）嘉兴月河桥拱形可以近似看作抛物线的一部分．在大桥截面1：1000的比例图上，跨度AB=5cm，拱高OC=0.9cm，线段DE表示河流宽度，DE∥AB，如图（1）在比例图上，以直线AB为x轴，抛物线的对称轴为y轴，以1cm作为数轴的单位长度，建立平面直角坐标系，如图（2）．（1）求出图（2）上以这一部分抛物线为图象的函数解析式，并写出自变量的取值范围；（2）如果DE与AB的距离OM=0.45cm，求河流宽度（备用数据：，计算结果精确到1米）．