…,but the only people who do succed are those who work hard为什么有only修饰了people而不用that（不是只能用that吗）

…,but the only people who do succed are those who work hard为什么有only修饰了people而不用that（不是只能用that吗）

那是指物时相对which 来说的.指人时,这里that,who 都可以,因为做主语