Use the Ratio Test or the Root Test to determine the values of x for which the series converges. The series is given by \sum_(k=1)^(\\infty)(7x^(k))/(8k^(3)). Which of the following options correctly describes the values of x for which the series converges?

A) x > 0
B) x < 0
C) x = 0
D) x can be any real number