Which of these series converges absolutely?
∑(−1)nn\sum \frac{(-1)^n}{n}∑n(−1)n
∑(−1)nn2\sum \frac{(-1)^n}{n^2}∑n2(−1)n
∑(−1)nn\sum \frac{(-1)^n}{\sqrt{n}}∑n(−1)n
∑cos(n)n2\sum \frac{\cos(n)}{n^2}∑n2cos(n)