Aparent that is heterozygous for both traits (aabb) can create how many different allele possibilities.

Distribute the A to the B and the b, then the a to the B and the b. You should get four different possible combinations: AB Ab aB ab. These would then be used to set up one side of a punnett square, and the other parent's genotype would be set up the same, then put on the other side of the punnett square. 

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The answer is b, as with an inference you make a statement with no evidence