单词拼写。

1. Her graduation from college was a great ____( 事件). I did not want to miss.

2. It's wrong for you to take ____( 躲避) under the tree in the storm.

3. Many people went to the ____( 灾难) area to help the victims as volunteers

    after the Wenchuan earthquake happened.

4. While I was cooking supper,the ____( 电) went off.

5. When the second earthquake happened,some of the___ ( 救援)workers and

    doctors were trapped under ruins.

采用电位滴定法测定水的碱度时，对于工业废水或含复杂组成的水样，可以PH4.4－4.5指示总碱度的滴定终点。