When the cap-seller shook his fists at the monkeys, they also did the same. This is mentioned in the text, "The cap-seller shook his fists at the monkeys. They also did the same." The monkeys copied his actions, which added a humorous element to the story.

Explanation:
The correct answer is option 'C' - They mimicked him.

Reasoning:
When the cap-seller shook his fists at the monkeys, they mimicked him. This means that the monkeys imitated the cap-seller's action of shaking his fists.

Detailed Explanation:
The story of the cap-seller and the monkeys is a popular folk tale. According to the story, a cap-seller was traveling through a forest, selling caps. He was tired and decided to take a nap under a tree.

While the cap-seller was sleeping, a group of mischievous monkeys came down from the trees and took all the caps from his basket. When the cap-seller woke up, he was shocked to find his caps missing.

In frustration, the cap-seller looked up and saw the monkeys sitting on the branches of the tree, wearing his caps. He came up with a clever idea to retrieve his caps. He took off his own cap, threw it on the ground, and shook his fists at the monkeys.

The monkeys, being curious creatures, imitated the cap-seller's actions. They took off the caps they were wearing and threw them on the ground while shaking their fists. The cap-seller quickly collected his caps and left the forest happily.

The monkeys' action of mimicking the cap-seller's gestures shows their intelligence and ability to imitate human behavior. It also highlights the cap-seller's quick thinking and cleverness in resolving the problem.

In conclusion, when the cap-seller shook his fists at the monkeys, they mimicked him by throwing off the caps they were wearing and shaking their fists as well. This allowed the cap-seller to retrieve his caps and continue his journey.