Which of the following is an example of incomplete dominance?   
A.  In a cross between tall plants and short plants, half the offspring are tall and half the offspring are short.   
B.  A cross between a black mouse and a white mouse produces a gray mouse.   
C.  A cross between a white cow and a red bull produces a calf with white hairs and red hairs.  
 D.  A blue-eyed child has one blue-eyed parent and one brown-eyed parent.