Which of the following statements is true regarding the Cauchy criterion for the convergence of a series?
1
The series converges if and only if the sequence of partial sums is bounded.
2
The series converges if and only if the sequence of partial sums is Cauchy.
3
The series converges if and only if the terms of the sequence are decreasing.
4
The series converges if and only if the terms of the sequence are positive.