While Moving into a New Apartment,Cole Needed to Hold the Door

While moving into a new apartment,Cole needed to hold the door open but he did not have a doorstop.Cole only had his heavy potted plant available and at first could not see how this would be useful.Then he realized he could use the plant as a doorstop to hold the door open.Cole solved this problem by

A) overcoming functional fixedness.
B) framing.
C) restructuring.
D) using a mental set.