下列级数中条件收敛的是(）A. sum_(n=1)^infty (-1)^n+1 (1)/(sqrt(n))B. sum_(n=1)^infty (-1)^n (1)/(n^2)C. sum_(n=1)^infty (-1)^n (n)/(n+1)D. sum_(n=1)^infty (-1)^n (1)/(n(n+1))

A. $\sum_{n=1}^{\infty} (-1)^{n+1} \frac{1}{\sqrt{n}}$

B. $\sum_{n=1}^{\infty} (-1)^{n} \frac{1}{n^2}$

C. $\sum_{n=1}^{\infty} (-1)^{n} \frac{n}{n+1}$

D. $\sum_{n=1}^{\infty} (-1)^{n} \frac{1}{n(n+1)}$