Correct is actually A.
From the options you can see that it is myFather.job not Job, so the correct syntax should be:
function Person() {
this.firstName = 'John';
}
Person.prototype = {
job: x => 'Developer',
};
const myFather = new Person();
const result = myFather.firstName + ' ' + myFather.job();
console.log(result);

If we run the correct syntax, always if it was not purposely written Job, the output will be John Developer

correct answer is C.

tested with below code -

function Person() {
this.firstName = 'John';
}
Person.prototype ={
Job: x => 'Developer'
};
const myFather = new Person();
const result =myFather.firstName + ' ' + myFather.job();