A system analyst designs a new system by

The correct answer is: A. identifying sub systems and the interfaces between sub systems.

A system analyst designs a new system by identifying the subsystems and the interfaces between them. This is done by understanding the current system and its requirements, and then identifying the different components that need to be included in the new system. The interfaces between the subsystems are then defined, which ensures that the different components of the system can communicate with each other.

Option B is incorrect because it describes the process of adapting an existing system to a new environment. This is not the same as designing a new system.

Option C is incorrect because it describes the process of developing a system as a large, single unit. This is not the same as designing a new system.

Option D is incorrect because it describes the process of proposing alternatives to the current system. This is not the same as designing a new system.

Option E is incorrect because it is not one of the possible answers.