Each face of a cube is painted either red or blue, each with probability 1 / 2. The color of each face is determined independently. What is the probability that the painted cube can be placed on a horizontal surface so that the four vertical faces are all the same color?
Answer Choices
A. \dfrac{1}{4}
B. \dfrac{5}{16}
C. \dfrac{3}{8}
D. \dfrac{7}{16}
E. \dfrac{1}{2}