1. Given: 10. class One { 11. public One foo() { return this; } 12. } 13. class Two extends One { 14. public One foo() { return this; } 15. } 16. class Three extends Two { 17. // insert method here 18. } Which two methods, inserted individually, correctly complete the Three class? (Choose two.)
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  1. public void foo() { }

  2. public int foo() { return 3; }

  3. public Two foo() { return this; }

  4. public One foo() { return this; }

  5. public Object foo() { return this; }

Show answer
Correct Option: C,D

AI Explanation

To answer this question, let's analyze each option:

Option A) public void foo() { } - This option is incorrect because it does not match the return type of the foo() method in the superclass Two.

Option B) public int foo() { return 3; } - This option is incorrect because it does not match the return type of the foo() method in the superclass Two.

Option C) public Two foo() { return this; } - This option is correct because it overrides the foo() method in the superclass Two with the same return type. The return type Two is a valid subtype of the return type One declared in the superclass.

Option D) public One foo() { return this; } - This option is correct because it overrides the foo() method in the superclass Two with the same return type. The return type One is the same as the return type declared in the superclass.

Option E) public Object foo() { return this; } - This option is incorrect because it does not match the return type of the foo() method in the superclass Two. Although Object is a superclass of all classes, it is not a valid subtype of the return type One declared in the superclass.

Therefore, the correct answers are Option C) public Two foo() { return this; } and Option D) public One foo() { return this; }.

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