Answer:
C
Explanation:
To send signals to the blood vessels to constrict or dilate , to increase or decrease blood flow respectively.
Random changes in allele frequency in a population are usually called genetic drift. The reason why this is the answer is because it is a very specific word which is used to describe exactly that - random changes in allele frequency.
All the other cases; answers, here aren't correct and don't apply.
The genes to be resistant to an antibiotic already exist in the bacteria's genes. Those whose phenotypes are resistant to the antibiotic will survive the antibiotic which kills the other non-antibiotic-resistant bacteria. The surviving bacteria will then asexually reproduce, producing more antibiotic-resistant bacteria.
