Arrange the cations Rb⁺, Be²⁺, and Sr²⁺ in order of increasing polarizing power.

A) Rb⁺ < Sr²⁺ < Be²⁺
B) Rb⁺ < Be²⁺ < Sr²⁺
C) Sr²⁺ < Rb⁺ < Be²⁺
D) Be²⁺ < Rb⁺ < Sr²⁺