Answer:
Long necks were a random genetic change and resulted in the gradual increase of organisms with long necks.
C. Medusa. Everything else on the list is a part of another creature, medusa is the only cnidarian here!
Because identical twins begin as a single fertilized egg that then separates, identical twins share 100 percent of genetic makeup.
<h3>IDENTICAL TWINS:</h3>
Identical twins are a type of twins characterized by their phenotypic similarity. They look so much alike that they are almost morphologically indistinguishable.
Their similarity emanates from their genetic content. Identical twins are formed when two sperms fertilize a single egg, which then splits into two.
Since identical twins begin as a single fertilized egg that then separates, this means that they share 100% of their genetic makeup.
Learn more about identical twins at: brainly.com/question/986349
The valves are responsible for preventing blood from flowing in the wrong direction, they are present in the veins, and the arteries don't need them because the aorta (biggest artery) pumps or in other words pushes it with such a force that no other force can change its direction, in the veins there is no structure present for pumping them as a result we have got valves so that they go in one direction...... the meaning of the word valve is to allow in one direction