A

$\displaystyle\sum\limits_{n=1}^{\infty}(a_n+b_n)$ 发散

B

$\displaystyle\sum\limits_{n=1}^{\infty}a_nb_n$ 发散

C

$\displaystyle\sum\limits_{n=1}^{\infty}(|a_n|+|b_n|)$ 发散

D

$\displaystyle\sum\limits_{n=1}^{\infty}(a_n^2+b_n^2)$ 发散