To answer this question, we need to understand what keywords are in the context of programming languages. Keywords are reserved words that have special meaning in a programming language and cannot be used as identifiers.
Let's go through each option to understand why it is correct or incorrect:
Option A) (D) & (E) - This option is incorrect. Both "extended" and "string" are keywords in some programming languages. "extended" is a keyword used in Java to indicate that a class is inheriting from another class, and "string" is a keyword used in several programming languages to represent a data type that stores a sequence of characters.
Option B) (A), (D) & (E) - This option is correct. "NULL" is not a keyword in most programming languages. It is often used to represent a null value or absence of a value, but it is not a reserved word. Both "extended" and "string" are keywords, as explained above.
Option C) (D) - This option is incorrect. As mentioned earlier, "extended" is a keyword in some programming languages.
Option D) (C), (D) & (E) - This option is incorrect. "protected" is a keyword in many programming languages, including Java and C++. It is used to specify that a member (e.g., variable or method) of a class can be accessed by subclasses.
The correct answer is option B. "NULL" is not a keyword, while "extended" and "string" are keywords in some programming languages.