Question 18: By using which model the software is developed in th series of Ans:- c)Spiral...

The Spiral model is a risk-driven software development process that combines the iterative nature of prototyping with the controlled and systematic aspects of the waterfall model, developing the software in a series of incremental loops (spirals).

Step-by-step Derivation:
Step 1: Analyze the phrase 'developed in the series'. In software engineering, this refers to an evolutionary or iterative approach where the project is broken down into smaller cycles.
Step 2: Evaluate Option A (Waterfall): This is a linear-sequential model, not a series of cycles.
Step 3: Evaluate Option B (Iterative): While it uses iterations, the 'Spiral' model is the specific formalization that defines the process as a series of expanding loops focusing on risk analysis.
Step 4: Evaluate Option C (Spiral): The Spiral model explicitly develops software in a series of iterations (spirals), where each loop involves planning, risk analysis, engineering, and evaluation.
Step 5: Evaluate Option D (Big Bang): This is an unstructured approach with no defined series or process.
Conclusion: The Spiral model is the most accurate description of software developed in a series of iterative cycles with risk management.