How old are you? — 英语阅读题

阅读短文，回答问题。 Today is May's birthday. Her friends come to her home. There is a big cake on the table. Mum asks May, "How old are you today?" May looks at the candles on the cake and says, "I'm nine. Look, there are nine candles on the cake!" Her friend Joe is ten years old. He says, "Happy Birthday, May!" Question: How old is May? 请用简短英语回答。