What is meant by functional analysis? When in the system life cycle is it accomplished? $($choose correct answer from below$)$

A$.$ An iterative process of translating system requirements into detailed design criteria and the subsequent identification of the resources required for system operation and support. Accomplished in conceptual and preliminary system design.

B$.$ To predetermine the function, form, cost and development schedule of the system. Accomplished in the detail design and development.

C$.$ Functional analysis, allocation of design$-$to requirements below system level, accomplishment of synthesis and trade$-$off studies, preparation of Types B$-$E specifications.

D$.$ An iterative process of translating system requirements into detailed design criteria and the subsequent identification of the resources required for system operation and support. Accomplished in detailed design and development.