Component testing focuses on verifying individual software components in isolation before they are integrated. The fundamental approach to this test level involves two key, interrelated practices. First is the principle of isolation (i), where the component under test is separated from other system components to ensure that defects found are localized to that component. Second, to enable this isolation, a test harness consisting of stubs and drivers (ii) is used. Drivers call the component under test, and stubs replace the components it calls, simulating the necessary interfaces. These two aspects together define the core strategy and environment for component testing.

B. This option is incomplete. While black-box testing (iii) is used, white-box testing (iv) is also a primary technique at the component level, and its omission is significant.

C. This option is highly incomplete. It only mentions one test design technique and ignores the fundamental environmental setup (isolation, stubs, drivers) and white-box testing.

D. This option is incomplete. It omits the foundational principle of isolation (i) and the valid use of black-box techniques (iii) derived from component specifications.

1. ISTQB® Certified Tester Foundation Level Syllabus 2018 (v3.1.1), Section 2.2.1 Component Testing, p. 16: "Component testing... is often done in isolation from the rest of the system... This may require stubs, drivers, and a test harness." This source directly links the principle of isolation (i) and the use of stubs and drivers (ii) as the primary setup for component testing.

2. Pezzè, M., & Young, M. (2008). Software testing and analysis: process, principles, and techniques. Wiley. Chapter 16, "Unit Testing," pp. 387-388. The text explains that to test a unit (component), it must be embedded in a test harness, which includes a driver program and stubs to substitute for modules called by the unit under test, thus enabling isolated testing.

3. Black, R., van Veenendaal, E., & Graham, D. (2019). Foundations of Software Testing: ISTQB Certification (4th ed.). Cengage Learning. Chapter 2, Section 2.2.1, "Component (Unit) Testing," p. 48. This section explicitly states, "To test a component in isolation, you need to simulate the components that send messages to it and are sent messages by it... These testing-support tools are called drivers and stubs."