When focusing a specimen you should always start with the SCANNING objective. Scanning objective is used to put the object you want to examine in focus. After proper focusing on the object, you can now switch to power objective.
Answer:
Basically, the Atrioventricular valves are Mitral and Tricuspid valves located between the atrium and ventricles. Their main functions is to “prevent the backflow of blood from the ventricles into the atrium during the ventricular contraction (systole).
Explanation:
<span>C) the force of gravity</span>