she is eight years old--------因为eight years old只能做表语,后面不加名词.
但是 :she is an eight-year-old girl 就对了,因为eight-year-old(做定语)后面必须加个名词,这里是可数名词单数.
she is eight years old--------因为eight years old只能做表语,后面不加名词.
但是 :she is an eight-year-old girl 就对了,因为eight-year-old(做定语)后面必须加个名词,这里是可数名词单数.