This is a question of the level of the college entrance examination. We use the method of classified discussion to solve it: 1 has two isolated points, so the isolated points must be 0,5, which is a situation. 2. There is an isolated point in A. There are two cases when the isolated point is 1 and 5, and one case when the isolated point is 234. In this way, when all cases add up, * * * has 8 subsets with isolated points, then the number of all 4 subsets without isolated points is: 30-8=22 (pieces).