Which of the following is caused by reproductive isolation within a species?
A. A decrease in gene flow
B. A decrease in genetic drift
C. An increase in genetic drift
D. An increase in gene flow

it will be A..

Explanation: Gene flow is the transfer of genes across two populations. This happens if there is mating between the two populations. However, this can be curtailed either by allopatry (due to geographical isolation) or sympatry (due to behavioral isolation) which results in reproductive isolation between the two populations. If the two population were of the same species, then the reproductive isolation can result in divergent speciation of the two populations.

the abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. the region occupied by the abdomen is termed the abdominal cavity. the stomach secretes acid and enzymes that digest food. ridges of muscle tissue called rugae line the stomach. the stomach muscles contract periodically, churning food to enhance digestion. the pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.

this transfer is call conjunction