The table format and symbols (++ and +) are derived directly from the ISO 26262 standard for functional safety in road vehicles. In this standard, the symbols indicate the level of recommendation for using a specific method to achieve a certain Automotive Safety Integrity Level (ASIL). '++' signifies that a method is "highly recommended," while '+' means it is "recommended." The standard requires that a suitable set of methods be chosen and their selection justified. Therefore, the supplier's tester must select an appropriate combination of methods, giving higher priority to those marked '++', and be prepared to rationalize their choices, especially if a highly recommended method is omitted.

B. This option incorrectly reverses the strength of the recommendations, suggesting '++' (highly recommended) is weaker than '+' (recommended).

C. This option uses imprecise and overly rigid language like "must be covered," which misrepresents the nature of a recommendation, and incorrectly interprets the symbols.

D. This option also incorrectly reverses the strength of the recommendations and uses inappropriate modal verbs ("must" and "can") that do not align with the standard's intent.

1. ISO 26262-6:2018, Road vehicles — Functional safety — Part 6: Product development at the software level.

Clause 5.3, "Notation in tables": This clause explicitly defines the meaning of the symbols used in the methods tables. It states:

"++" indicates that the method is highly recommended for the corresponding ASIL.

"+" indicates that the method is recommended for the corresponding ASIL.

Clause 5.4.2, "General requirements": This clause states, "The selection of measures shall be justified." This supports the part of the correct answer that mentions the need to "explain his choice."

2. Mariani, L., & Pastore, F. (2012). A Survey on the Role of Testing in the new ISO 26262 Functional Safety Standard. Politecnico di Milano, Tech. Rep.

Section 3, "The ISO 26262 Standard": This paper discusses the structure of the standard, explaining that the tables provide "recommendations about the techniques that should be adopted for the different ASILs," reinforcing that '++' and '+' are recommendations of different strengths, not absolute mandates or options.

3. University of Stuttgart, Course: "Safety in Automotive Engineering" (Sicherheit in der Fahrzeugtechnik).

Lecture notes on ISO 26262: Course materials frequently explain that the selection of methods from the standard's tables is a key part of the safety argument. They emphasize that while "highly recommended" (++) methods are not strictly mandatory, their non-use requires a rigorous and documented justification, thus they must be given "higher consideration."