Step 1: Recall the diagonal test.
Designers check whether one rectangle is a scaled copy of another by placing them corner to corner and extending a single diagonal line from the shared corner through the far corner of the larger one.
Step 2: Apply it here.
Line up image P's bottom-left corner with each option's bottom-left corner, then draw the diagonal from that shared corner through P's own top-right corner.
Step 3: Check where each option's far corner falls.
For a true scaled copy, its own top-right corner must land exactly on this diagonal line, since scaling moves a corner only along the line joining it to the shared corner.
Step 4: Identify the match.
Only image C's top-right corner falls on this diagonal line drawn from P; A, B and D each fall off the line, in the direction of whichever way they have been stretched.
\[ \boxed{\text{C}} \]