The verified answer is A .

This constructor function runs when new Person() is called:

function Person() {

this.firstName = " John " ;

}

So this line:

const myFather = new Person();

creates an object like this:

{

firstName: " John "

}

Then the prototype is assigned a method named job:

Person.prototype = {

job: x = > " Developer "

};

Because myFather is created from Person, it can access properties and methods from Person.prototype.

So:

myFather.firstName

returns:

" John "

And:

myFather.job()

returns:

" Developer "

Therefore:

const result = myFather.firstName + " " + myFather.job();

becomes:

const result = " John " + " " + " Developer " ;

Final value:

" John Developer "

Option B is incorrect because job() returns " Developer " , not undefined.

Option C is incorrect because job exists on Person.prototype, so it is callable.

Option D is incorrect because firstName is assigned inside the constructor.

Therefore, the verified answer is A .