这道题目要注意三个要点：

1. 动词短语suffer from；

2. 介词from+whose构成的非限制性定语从句。

3. 定语从句中的whose作effects的定语。

首先将这个题目改为两个简单句：

Last month, part of Southeast Asia was struck by floods. People are still suffering from their effects.

注意：在后一句中，与“洪水”floods有关系的词是their。由于their是用作定语，所以将其变为关系词代词whose（也有人称之为关系形容词）而构成from whose effects来引导定语从句。

Last month, part of Southeast Asia was struck by floods, from whose effects people are still suffering．

再举一个将两个简单句合并成一个复合句的例子：

Lao Li was a quick-witted undergrounder. He cleverly escaped from his captors. 老李是一个机智的地下工作者，他巧妙地从捕获他的人手中逃脱了。

后一句中的his作定语且与前句中的undergrounder有关系，所以关系代词要用whose。变为定语从句便是：

Lao Li was a quick-witted undergrounder, from whose captors he cleverly escaped.