in order: alternating series, nth term, ratio, geometric series
The 4th series is the only one that is geometric. With that taken, the first is the only alternating (signs) series. We can apply the nth term test to the n2 series, because the limn→∞ n2 ≠ 0, so the series diverges. The ratio of the n+1st term to the nth term in 2n/n! , 2/(n+1), is sufficient to show convergence.