Final answer:
Option (D), Jess building a bridge to Terabithia symbolizes his personal growth and way of coping with the loss of his friend Leslie, by honoring her creativity and memory.
Step-by-step explanation:
At the end of the story, the fact that Jess is building a bridge to Terabithia is symbolically significant. It does not concern transportation or a school project, nor does it represent a fear of bridges. Rather, it signifies Jess's growth and his way of coping with the loss of Leslie, his dear friend.
By constructing the bridge, Jess is honoring Leslie's memory and creativity, while also allowing himself to heal and open up the magical world of Terabithia to his younger sister. This act demonstrates Jess's determination, his deep love for Leslie, and his maturity in dealing with the reality of loss and grief.