根据句意和首字母补全单词。

1. On the morning of August 5, 2006, there was a _____ fire in the big city.

2. When the policemen _____ here, the hurt man was taken to the hospital.

3. Yesterday Lucy _____  into a river while she was playing with her friends near the river.

4. Please wear a heavy coat to protect yourself _____ wind and snow.

5. _____ others were using big searchlights to look into the rooms.

如图所示，正方形线框abcd放在光滑绝缘的水平面上，其质量m=0.5 kg、电阻R=0.5 Ω、边长L=0.5 m。M，N分别为线框ad，bc边的中点。图示两个虚线区域内分别有竖直向下和竖直向上的匀强磁场，磁感应强度均为B=1 T，PQ为其分界线，线框从图示位置以初速度v₀=2 m/s向右滑动，当MN 与PQ重合时，线框的瞬时速度方向仍然向右，求：

(1)线框由图示位置运动到MN与PQ重合的过程中磁通量的变化量；

(2)线框运动过程中最大加速度的大小。