B 
Four fair six-sided dice are rolled. What is the probability that at least three of the four dice show the same value? 
Options:
a: $\frac{1}{36}$ 
b: $\frac{7}{72}$ 
c: $\frac{1}{9}$ 
d: $\frac{5}{36}$ 
e: $\frac{1}{6}$ 