节日文化理解 — 英语阅读题

Read and answer. 阅读短文，回答问题。 Lily's Favourite Festival Lily is a girl from Shanghai. Her favourite festival is the Mid-Autumn Festival. It comes in September or October. On that day, the moon is big and round. In the evening, Lily's family sit in the garden. They watch the beautiful moon together. Grandma tells them a story about Chang'e. Everyone eats mooncakes. Lily likes the ones with red bean best. "The round moon and the round mooncakes mean family members get together," Grandma says. Lily feels happy and warm at this festival. Question: Why are the moon and the mooncakes round at the Mid-Autumn Festival? （为什么中秋节时月亮和月饼都是圆的？）请根据短文用英语或中文简短回答。