Which of the following series is conditionally convergent?\\
(A) $\sum _ { k = 1 } ^ { \infty } ( - 1 ) ^ { k } \frac { 5 } { k ^ { 3 } + 1 }$\\
(B) $\sum _ { k = 1 } ^ { \infty } ( - 1 ) ^ { k } \frac { 5 } { k + 1 }$\\
(C) $\sum _ { k = 1 } ^ { \infty } ( - 1 ) ^ { k } \frac { 5 k } { k + 1 }$\\
(D) $\sum _ { k = 1 } ^ { \infty } ( - 1 ) ^ { k } \frac { 5 k ^ { 2 } } { k + 1 }$