根据短文内容，判断正误。

Mary, Jane and May are very good friends. Mary is shorter than May, May is heavier than Jane. Jane is thinner than Mary. How old are they? Mary is 7 years old. Jane is one year younger than May and May is 9 years old. They study at Qing Lan Primary School. Mary likes English, Jane likes math and May likes music. They all study hard.