题目

按要求完成句子；句型转换,每空一词。 1. It is raining heavily now. (改为感叹句)   __________ ___________ it is raining now! 2. They grow rice in South China.（变被动语态） Rice                    inSouth China 3. Shoes with lights are used for seeing in the dark. (对画线部分提问) __________are shoes with lights __________ for? 4. Are you busy doing your homework now? He asked me.（合并为宾语从句） He asked me                    was busy doing my homework then. 5. The door was locked when we arrived. (改（2004•聊城模拟）如图，正方形ABCD中，有一直径为BC的半圆，BC=2cm，现有两点E、F，分别从点B、点A同时出发，点E沿线段BA以1cm/s的速度向点A运动，点F沿折线A-D-C以2cm/s的速度向点C运动，设点E离开点B的时间为t（秒）．（1）当t为何值时，线段EF与BC平行？（2）设1＜t＜2，当t为何值时，EF与半圆相切？（3）1≤t＜2时，设EF与AC相交于点P，问点E、F运动时，点P的位置是否发生变化？若发生变化，请说明理由；若不发生变化，请给予证明，并求AP：PC的值．