Which of the Following Series Are Convergent, but Not Absolutely $\sum _ { n = 1 } ^ { \infty } ( - 1 ) ^ { n + 1 } \frac { n + 2 } { n ^ { 2 } + 1 }$

Multiple Choice

Which of the following series are convergent, but not absolutely convergent?
1) $\sum _ { n = 1 } ^ { \infty } ( - 1 ) ^ { n + 1 } \frac { n + 2 } { n ^ { 2 } + 1 }$
2) $\sum _ { n = 1 } ^ { \infty } \frac { ( - 1 ) ^ { n } } { n ^ { 4 } }$
3) $\sum _ { n = 1 } ^ { \infty } \frac { ( - 1 ) ^ { n } n } { n + 1 }$

A) None
B) 1
C) 2
D) 3
E) 1, 2
F) 1, 3
G) 2, 3
H) 1, 2, 3