Which of the following alternating series diverges?

MATHEMATICS · Single correct · AP · Calculus BC · Infinite Sequences and Series · Infinite Sequences and Series

Problem

Which of the following alternating series diverges? (a)

\displaystyle \sum_{n=1}^{\infty} (-1)^{n+1}\,\frac{1}{\sqrt{n}}

(b)

\displaystyle \sum_{n=1}^{\infty} (-1)^{n}\,\frac{n}{n+1}

(c)

\displaystyle \sum_{n=1}^{\infty} (-1)^{n+1}\,\frac{\ln n}{n}

(d)

\displaystyle \sum_{n=1}^{\infty} (-1)^{n+1}\,\frac{1}{n}