To answer this question, we need to understand the concept of method overriding and access modifiers in Java.
In line 2, the method blipvert is defined in the Blip class with the protected access modifier. This means that the method can be accessed by any class within the same package or by any subclass, regardless of the package it belongs to.
In line 4, the Vert class extends the Blip class. This means that the Vert class inherits all the accessible members (fields and methods) of the Blip class, including the blipvert method.
We are asked to determine which methods, when inserted at line 5, will compile correctly.
Option A) public int blipvert(int x) { return 0; }
This method has the same signature as the method in the Blip class, and it has a more accessible access modifier (public). Since a subclass is allowed to have a method with a more accessible access modifier, this method will compile.
Option B) private int blipvert(int x) { return 0; }
This method has the same signature as the method in the Blip class, but it has a less accessible access modifier (private). A subclass is not allowed to have a method with a less accessible access modifier, so this method will not compile.
Option C) private int blipvert(long x) { return 0; }
This method has a different parameter type (long) compared to the method in the Blip class (int). This is method overloading, not overriding. It will compile correctly.
Option D) protected long blipvert(int x) { return 0; }
This method has the same signature as the method in the Blip class, but it has a different return type (long) compared to the method in the Blip class (int). This is method overloading, not overriding. It will compile correctly.
Option E) protected int blipvert(long x) { return 0; }
This method has a different parameter type (long) compared to the method in the Blip class (int). This is method overloading, not overriding. It will compile correctly.
Option F) protected long blipvert(long x) { return 0; }
This method has the same parameter type and return type as the method in the Blip class. It is an exact match for the overridden method, and it has the same or more accessible access modifier (protected). It will compile correctly.
Therefore, the five methods that will compile correctly when inserted at line 5 are: A, C, E, F.