Which one of the following statements regarding the waterfall model for the software life cycle is FALSE?

a$.$ The waterfal model is a very popular model for software development.

b$.$ The analysis phase must be completed before the design pha se can start.

c$.$ The implementation phase cannot star$1$ before the design phase is complete.

d$.$ The $$ phase can be done at any time during the process, ie the design phase cen be tested cven before the implementation phase is complete.