Protected base class members cannot be accessed by: a. friends of the base class.

b. friends of derived classes.

c. Functions that are not derived-class member functions.

d. Functions that are neither friends of the base class, derived-class member functions nor friends of a derived class.

The answer is "Option d".

Explanation:

This class members can be accessed by their member and the friend of there class, It is also known as the Members of the derived class from the basic class can be accessed by the protected and non-static member of the base class, and wrong choices can be described as follows:

Option a and Option b both are wrong because non-static member can't be accessed by there base or derived class. In option c, It is wrong because the function is a member function of the derived class.