Question

differ has the same or almost the same meaning as: treat extend vary adjoin

Explanation:

"Differ" means to be unlike or dissimilar. "Vary" also means to be different or change in amount, level, or character. The other words - "treat" (deal with or handle), "extend" (make longer or larger), "adjoin" (be next to or joined with) - do not have similar meanings.

Answer:

C. vary