Under which of the following circumstances would the allele frequencies of two populations be very different a. if there is a large amount of genetic drift b. if there is a large amount of gene flow c. if the selective pressures are different d. if the populations have healthy reproductive rates

Option A

Explanation:

The relative change in frequency of allele is called genetic drift. Genetic drift is basically observed in a population of small size where there are high chances of loss of allele that occur in irregular manner. Genetic drift continues till the allele  (involved in the drift) is either lost or becomes the only gene with in the population.  

Hence, option A is the correct answer

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.