Final answer:
The question involves formal grammar concepts and the roles of non-terminal symbols. There could be null productions or non-terminals in any sequential form within the rules. However, the answer to the question posed is D because not enough information is provided to determine a clear answer.
Step-by-step explanation:
The question deals with concepts in formal grammar, specifically relating to non-terminal symbols in the context of computing or computational linguistics. When discussing grammars, we are typically referring to the formal rules that describe how languages are constructed. These rules are critical in the design of compilers and interpreters for programming languages.
Answer A suggests that a non-terminal A cannot derive any string of terminals. This statement is accurate because in a formal grammar, it is possible to have what's known as a null production, where a non-terminal does not lead to any terminal symbol. Answer B suggests that a non-terminal A can be present in any sequential form. Depending on the specific rules of the grammar, this could be true, as non-terminal symbols can appear in many different parts of a production.
However, the question as phrased is unclear, and neither of these explanations directly deal with the concept of mixed sentence constructions, syntax, or mutual exclusivity in grammar rules. The question seems to conflate grammatical structures in natural language with formal grammar in computational contexts. Therefore, the most accurate response, given the information contained within the question, is D. Not enough information given to determine the answer.