One day, there was a thirsty crow flying here and there looking for water. Unfortunately, he couldn’t find any. Finally, he saw a water pitcher under a tree. Sadly, the water in the pitcher was very little, and the neck of the pitcher was too narrow for the crow to reach the water. Cleverly, the crow began picking up pebbles and dropping them one by one into the pitcher. Slowly, the water in the pitcher rose, and the crow could drink until he was satisfied.
1. What is the main theme of the story?