Correct Answer: (c) a trial version is available only at the end of the project
Waterfall model is a Software Development Life Cycle. This process model has the following steps which are executed one after the other like waterfall.
Phase 1: Requirement Specification
Phase 2: Design
Phase 3: Construction
Phase 4. Integration
Phase 5: Testing
Phase 6: Debugging
Phase 7. Installation
Phase 8: Maintenance
One of the disadvantages of this model is that the trial version of the software is available only at the last.
Reference: B. G. Geetha, Dutt Saikat, Chandramouli Subramanian, Chandramouli Seetharaman- Software Engineering- Pearson Education (2015)