The answer is C. At first the child misjudges the elderly neighbor when he fears her, and is happy with their new friendship when she helps him.
A has misjudgment but no happiness.
B doesn't match at all
D doesn't say that the rivals misjudged their rivalry or were happy at any point.
Personification is going to be your answer. Don't read the rest because I am only doing this to reach the max character needed.
A) Nail
You use thread with a needle and a nail with a hammer
