按要求改写下列句子。

1．She has been working for 20 hours.（改为一般疑问句，并作否定回答）

             she       working for 20 hours?No,              .

2．I've been skating since l was six years old.（对画线部分提问）

                           you been skating?

3．Tom ran for one hour.（用现在完成进行时改写）

      Tom                     for one hour.

4.   We have been learning English for three years．（改为同义句）

      We have been learning English                            .

5.   I started playing tennis when I was seven years old. （改为同义句） 

      I started playing tennis                            seven.

软件的需求分析阶段的工作，可以概括为四个方面： 【4】 、需求分析、编写需求规格说明书和需求评审。