有毒物质会通过食物链富集．在河水、浮游生物、鱼、鸭中，有毒物质含量最多的是（　　）

A．河水

B．浮游生物

C．鱼

D．鸭

Ravi, like many project (1) , had studied the waterfall model of software development as the primary software life-cycle (2) . He was all set to use it for an upcoming project, his first assignment. However, Ravi found that the waterfall model could not be used because the customer wanted the software delivered in stages, something that implied that the system had to be delivered and built in (3) and not as (4) .

The situation in many other projects is not very different. The real world rarely presents a problem in which a standard process, or the process used in a previous project, is the best choice. To be the most suitable, an existing process must be (5) to the new problem.

A development process, even after tailoring, generally cannot handle change requests. To accommodate change requests without losing control of the project, you must supplement the development process with a requirement change management process.

（4）处填（）。

A．parts

B．modules

C．software

D．a whole