The correct testing tasks are to verify application functionality, find defects, and ensure the app meets design specifications. Testing occurs after development produces a build and before acceptance or deployment decisions are made. Its purpose is to compare the implemented application against expected behavior, requirements, and design specifications. Option A is correct because functional testing confirms that user workflows, controls, validation rules, scripts, and page interactions work as intended. Option C is correct because defect discovery is a core testing responsibility; testers identify failures, inconsistencies, regressions, and unexpected behavior so the development team can correct them. Option D is correct because the app must be evaluated against the documented design, including layout, navigation, responsiveness, accessibility expectations, and feature behavior. Asking customers to submit bugs or feature requests is a feedback or product-management activity, not the primary task of an internal test cycle immediately following a development release. Checking syntax errors is primarily handled during development, linting, editing, or build processing; a released test build should already parse and execute sufficiently for functional testing. References/topics: application lifecycle management, test phase, defect detection, functional testing, design specification validation.