In Horses,black Coat Color Is Influenced by the Dominant Allele

Multiple Choice

In horses,black coat color is influenced by the dominant allele (B) ,and chestnut coat color by the recessive allele (b) .Trotting gait is due to a dominant gene (T) ,pacing gait to the recessive allele (t) .Give the phenotype and genotype of the horse you would use in a testcross to determine the genotype of a black trotter.  

A) Black pacer, BB tt
B) Black trotter, BB TT
C) Chestnut trotter, Bb Tt
D) Chestnut pacer, bb tt
E) Chestnut pacer, Bb tt