The mating of a horse and a donkey produces a mule, which is a viable offspring that is infertile. we would conclude that

a. a house and a donkey are members of the same species

b. a mule can fall into the species lines of both a mule and a horse.

c. a horse and a donkey produce s fertile offspring, not a infertile one

d. a horse and a donkey are not of the same species

D. A horse and a donkey are not of the same species

Explanation:

Two organisms can be said to belong to the same species if they are able interbreed to produce not just a viable offspring but also a fertile offspring. Members belonging to the same species should able to interbreed to produce offspring that are both viable and fertile, according to the Biological Species Concept.

A mule is a viable offspring of a cross between a female horse and a male donkey. However, the mule is sterile. This plainly suggests that a horse and a donkey are not of the same species. Donkeys and Horses have different numbers of chromosomes.  

D. A horse and a donkey are not of the same species

Explanation:

A mule is an animal produced by the fertilization of a donkey's and horse's gametes. The mule is usually sterile i.e. it cannot reproduce. Sexually-reproducing organisms undergoes meiosis to produce gametes. Meiosis reduces the chromosomal number of the daughter cells (gametes) by half.

It is important to note that organisms of different species contains different number of chromosomes in their cells. For an organism to undergo meiosis, it must possess a complete set of chromosomes

(each set from each parent) as each set will be separated into the resulting gametes. The donkey and horse are different species of diploid animals with 62 and 64 chromosomes respectively.

They undergo meiosis to produce gametes with 31 and 32 chromosomes respectively, which fuses to produce the mule with 63 chromosomes. This 63 number of chromosomes is an incomplete set, hence, cannot undergo meiosis. This is the reason why the mule is sterile or infertile. In a nutshell, the horse and donkey are not of the same species, hence, will contain different chromosome number. If they produce a viable offspring called mule, it will have an Incomplete set of chromosomes which cannot be divided equally into gametes during meiosis. Hence, mules don't undergo meiosis and as a result, unable to reproduce.