Martina does not think cross species breeding should be allowed. which of the following facts best supports her opinion?
a) mules are stronger and have more endurance than horses.
b) genetically engineered proteins can fight disease.
c)quarter horses bred to compete in rodeos are fast and strong.
d) mules cannot reproduce because they have an odd number of chromosomes.

(D). Mules cannot reproduce because they have an odd number of chromosomes.

Explanation:

Cross species breeding may be defined as the process of breeding between two different species. For example, Mule is obtained by the breeding between male donkey and female horse.

Mules have odd  number of chromosomes and they are sterile. This is because, odd number of chromosomes leads to non-disjunction and formation of abnormal chromosomal separation during gamete formation. Due to this, non-functional gametes are formed during meiosis and mules cannot reproduce.

Thus, the correct answer is option (D).