Final answer:
Zach's nickname for Dewey was 'Dewdrop.' This nickname indicates a kind of affectionate or teasing relationship between the characters and is used to depict the closeness of their bond.
Step-by-step explanation:
Zach's nickname for Dewey was d) Dewdrop. This nickname is a term of endearment and closely ties into the playful and affectionate dynamic that is often depicted between characters in literature. Nicknames often symbolize a special bond or intimacy among characters, and the selection of 'Dewdrop' suggests a certain level of fondness and perhaps even a gentle teasing nature within their relationship. By choosing this nickname, Zach demonstrates a personal connection to Dewey that is unique to their interaction.