How to apply the principle of encapsulation in OOP?

Question

The principle of encapsulation is used to be applicated through which good habits ?

Accepted Answer

Declare all the attributes of a class with *private* visibility.

Answer

Declare all the methods of a class with *private* visibility.

Answer

Declare all the methods of a class with *protected* visibility.

Answer

Declare all the members of a class with *private* visibility.

Question from the Object-oriented programming - Fundamentals test