Which method or operator should you add to the function?

You are creating a custom function. You pass an object named testObj to the function as a parameter. You do not use inheritance through the functions.
The function must establish whether testObj inherits from another object named parentObj.
You need to ensure that the function performs as required.
Which method or operator should you add to the function?
A. parentObj.instanceof(testObj)
B. testObj.isPrototypeOf(parentObj)
C. testObj.instanceof(parentObj)
D. parentObj.isPrototypeOf(testObj)