Which of the following statements correctly contrasts the listed pairs: testing versus debugging, two-tier versus three-tier architecture, alpha versus beta testing, and static versus dynamic testing?

Introduction / Context:
Software engineering uses many paired concepts that are related but distinct. Understanding the differences between testing and debugging, two-tier and three-tier architecture, alpha and beta testing, and static and dynamic testing is essential for clear communication in projects. This question bundles these pairs and asks which option correctly contrasts them in a concise way.

Given Data / Assumptions:
- Testing is the activity of executing software to reveal defects, while debugging is the activity of finding and fixing the causes of those defects.
- Two-tier and three-tier architectures describe how responsibilities are split across client, application, and data layers.
- Alpha and beta testing are stages of acceptance testing carried out by different types of users in different environments.
- Static testing evaluates artefacts such as code or documents without running the software, whereas dynamic testing involves execution.

Concept / Approach:
To answer correctly, each part of the option must accurately describe the pair. Testing versus debugging focuses on execution to find defects versus analysis and fix. Two-tier versus three-tier focuses on whether there is only a client and database or an additional application server layer. Alpha versus beta testing focuses on internal users at the developer site versus external users or customers in their own environment. Static versus dynamic testing distinguishes non execution review and analysis from execution based validation. Option A is the only one that correctly captures all of these distinctions at once.

Step-by-Step Solution:
1. For testing and debugging: Testing aims to find defects by executing the software with representative inputs. Debugging starts after a defect is observed and involves tracing, analysing, and fixing the root cause in code or configuration. 2. For two-tier versus three-tier architecture: In a two-tier setup, a thick client communicates directly with a database server. In a three-tier setup, a middle application server layer sits between the client and the database to handle business logic and communication. 3. For alpha versus beta testing: Alpha testing usually occurs at the developer or vendor site with internal staff or a small invited group simulating end users. Beta testing involves releasing the software to a limited number of real customers to use in their own environment. 4. For static versus dynamic testing: Static testing checks artefacts (such as requirements, design documents, and source code) without executing the program, using techniques like reviews, walkthroughs, and static analysis. Dynamic testing executes the software and observes outputs, performance, and behaviour. 5. Option A describes all four pairs in this way, matching standard definitions.

Verification / Alternative check:
Standard testing and software engineering textbooks and certification syllabi define testing as execution based and debugging as fix based, while also describing two-tier and three-tier architectures with examples such as client database applications versus web applications with separate application servers. They place alpha testing before beta testing, with alpha done internally and beta done in the field by external users. Finally, they classify reviews and static analysis under static testing, and test execution under dynamic testing. Comparing these reference descriptions with the statements in option A confirms that it is accurate.

Why Other Options Are Wrong:
Option B incorrectly states that testing and debugging are identical and that static testing always involves execution, both of which contradict definitions. Option C incorrectly claims that testing is performed only after debugging and misdescribes where alpha testing occurs. Option D reverses the roles of testing and debugging and makes incorrect statements about architecture layers and the order of alpha and beta testing. None of these options correctly represent all four concept pairs. Only option A consistently matches recognised definitions.

Common Pitfalls:
A common misconception is to treat testing and debugging as a single combined activity, when they actually require different skills and mindsets. Developers may also loosely use the terms alpha and beta without respecting their usual distinction in location and user type. Similarly, many people think of static testing as something only automated tools can do, ignoring the value of human reviews. This question encourages more precise terminology, which improves communication in technical discussions and project documentation.

Final Answer:
The correct statement is that testing executes software to find defects, debugging analyses and fixes defects; two-tier has client and database, three-tier adds an application server; alpha testing is done internally at the developer's site, beta testing is done by external users; static testing examines artefacts without execution, dynamic testing involves running the software.