Which type of vessel normally contains valves that prevent the backward flow of materials

answer; /// i believe the correct answer is (reactants);

meiosis is the first to occur after the nuclei of opposite of opposite mating types fuse

brain development. a child's brain undergoes an amazing period of development from birth to three—producing more than a million neural connections each second. the development of the brain is influenced by many factors, including a child's relationships, experiences and environment.

explanation: