The correct answer is:
D. It shows the speaker is able to communicate with his or her mother once again.
The metaphor "the wall shrinks—it is a football that I can kick away" suggests that the emotional distance or barriers (the wall) between the speaker and the mother is lessening, allowing for better communication. By comparing the wall to a football that can be kicked away, it implies that the speaker feels empowered to overcome the barriers that hinder their connection with the mother, portraying a moment of understanding and closeness.