The central principle which derives from McGregor’s Theory is:

(d) >>>>>>>>>>>>>>>> Integration

My answer is option (D) Integration

The central principle which derives from McGregor’s Theory is:

(d) Integration

Agree with my colleagues 

Thanks for invitation

My answer option d)  <<<<<<<<<<<<<<<<<<<<<<,,,,,

(d) Integration is the right answer........................

>>>> The answer will be (d) Integration

(d) Integration is the answer.