hi, i have a set of ap practice problems to do, and theres a topic on one of these questions that we havent covered in class. could anyone help me out please?

which of the following series converge?

I.) the summation from 1 to infinity of (k)/(n^2) where k is a constant

II.) the summation from 1 to infinity of (-1)^n/(n^1/2)

III.) the summation from 1 to infinity of (0.4)^(n-1)

a.) I only

b.) II only

c.) III only

d.) I and III

e.) I, II, and III

thanks so much