Final answer:
A strictly context-free language adheres to the Chomsky hierarchy as a context-free language, excluding context-sensitive rules, unrestricted grammars, and regular expressions.
Step-by-step explanation:
To determine if a language is strictly context-free, it's essential to review its characteristics against known language and grammar frameworks. A strictly context-free language does not use regular expressions (option a) since these belong to a subset called regular languages, align with the Chomsky hierarchy (option b), specifically the context-free level, and does not contain context-sensitive rules (option c), as those are part of the context-sensitive languages. Furthermore, they do not conform to unrestricted grammars (option d) because unrestricted grammars allow for rules that are not permitted in strictly context-free languages.Context-free languages are formally defined by context-free grammars that generate them. The rules in context-free grammars have a single non-terminal symbol on the left-hand side and some combination of non-terminal and terminal symbols on the right-hand side, without requiring any specific context for the rules to be applied—a characteristic that context-sensitive languages do not share. So the requirements for a language to be strictly context-free are adherence to the Chomsky hierarchy's context-free level and the exclusion of context-sensitive rules and unrestricted grammars.