Answer:
Notes to the teacher: Lub Dub
There are two sounds heard during each heart beat. These are called Lub-Dub noises by doctors. When the valves between the upper chambers (atria) and lower chambers (ventricles) close, a "lub" sound is heard. ... The heart contains valves which direct the flow of blood in one direction.
Step-by-step explanation:
pls give me brainless