This is a question of choosing a school or a teacher. Good schools have a high proportion of good teachers, but there are also poor teachers. I think the most accurate answer is to choose a good "fund manager"

Each fund company has about 10 funds, and generally each type of fund has some, so as to keep the variety intact. Funds are divided into four categories: stock funds, balanced funds, bond funds and monetary funds, and the risk and return are decreasing in turn.