To answer this question, you need to understand the access modifiers in Java.

The access modifiers in Java are used to control the visibility and accessibility of classes, methods, and variables. There are four access modifiers in Java:

1. public: Allows access from anywhere, including outside the package.
2. protected: Allows access from within the same package and from subclasses, even if they are in different packages.
3. private: Limits access to within the same class only.
4. Default (no modifier): Allows access from within the same package only.

In this question, the keyword that can protect a class in a package from accessibility by the classes outside the package is the default access modifier (no keyword at all). When a class does not have an access modifier specified, it is considered to have default access. This means that the class can be accessed only by other classes within the same package.

Option A) private: This option is incorrect because the private access modifier restricts access to within the same class, not the same package. Option B) final: This option is incorrect because the final keyword is used to prevent a class from being subclassed, but it does not restrict access from outside the package. Option C) protected: This option is incorrect because the protected access modifier allows access from subclasses and classes within the same package, but it does not restrict access from outside the package. Option D) Don't use any keyword at all (make it default): This option is correct. By not specifying any access modifier, the class will have default access and can only be accessed by other classes within the same package.

Therefore, the correct answer is option D.

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To determine which options are not keywords, we need to understand what keywords are in programming.

Keywords are predefined reserved words in a programming language that have special meanings and cannot be used as variable names or identifiers. These keywords are typically used to define the syntax and structure of the programming language.

Now, let's go through each option to determine which ones are not keywords:

Option A) (D) & (E) - This option includes (D) and (E) as not keywords. (D) is "extended" and (E) is "string". "extended" is not a keyword, but "string" is a keyword in many programming languages.

Option B) (A), (D) & (E) - This option includes (A), (D), and (E) as not keywords. We have already determined that (D) is not a keyword, and (A) is "NULL" which is also not a keyword. However, (E) is "string" which is a keyword.

Option C) (D) - This option includes (D) as not a keyword, which is correct.

Option D) (C), (D) & (E) - This option includes (C), (D), and (E) as not keywords. We have already determined that (D) is not a keyword. (C) is "protected" which is a keyword in many programming languages. (E) is "string" which is also a keyword.

Based on the above analysis, the correct answer is B. The options (A), (D), and (E) are not keywords.

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• Wrong explanation