Answer:
The duplication of a cluster of four Hox genes is equally likely as the duplication of a single Hox gene.
Explanation:
This comes from the definition of the parsimony principle, which is the action of choosing the simplest scientific explanation fitting the given evidence, meaning that all other elements are equal when evaluating the hypothesis. In biology the best hypothesis is the one that requires the fewest evolutionary changes.
Since three independent duplications of an individual Hox gene is in evolutionary terms, more complex than a single duplication or a cluster, then that hypothesis would be the most parsimonious.
Compounds consist of atoms of different elements. In compound the atoms are present in fixed proportion. By changing the proportion compound will changed. For example,
Nitrogen and oxygen reacted to form the compound. By changing the proportion both will form different compound.
NO₂
Nitrogen dioxide consist of one atom of nitrogen and two atoms of oxygen. Their ration is 1 :2
NO
In nitric oxide one atom of oxygen and one atom of nitrogen are present.
Their ratio is 1 : 1.
N₂O
Nitrous oxide consist of two nitrogen atoms and one oxygen. Their ratio is
2 : 1
N₂O₄
Dinitrogen tetroxide consist of two nitrogen atoms and four oxygen atoms. Their ratio will written as 2 : 4
N₂O₅
Dinitrogen pentoxide consist of two nitrogen atoms and five oxygen atoms. Their ratio will written as 2 : 5
Natural Selection proposes that organisms that are better adapted to their environment are able to survive and reproduce.
Even though these frogs are the same species, their shades of green is what helps them to survive in their habitat. In this case, frogs with a lighter shade of green are able to be seen by predators easier, whereas frogs with darker shades are able to blend in (camouflage) more with their surroundings. After a period of time, due to them being easily seen, lighter-shaded green frogs will die off.
To anseer your question, natural selection would have a gradual affect on the frequency of the alleles. Lighter-green allele frequencies would eventually cut off, and darker-green allele frequencies will increase.
Hopefully the following image will help:
As seen in the image, (please forgive the quality, as I had drawn this on some random kids drawing site on the internet...) you can see the affects of natural selection on the allele frequencies. The brighter-green shades gradually decrease over time, as the darker shades increase.
Hope you find this helpful.
B, is the answer. I believe.