what did valli see on her way that made her laugh

Valli saw a young cow running very fast right in front of the bus with its tail held high in the air. The bus driver sounded the horn repeatedly, trying to get the cow to move out of the way, but the more the horn honked, the more frightened the cow became, causing it to run even faster. This whole scene seemed very funny to Valli, and she laughed heartily until there were tears in her eyes.