The mass of an atom is contained primarily in its NUCLEUS.
An atom is made up of three sub particles, which are proton, neutrons and electrons. The proton and the neutrons are located in the nucleus of the atom while the electron  are located outside the nucleus where they move about in continuous motion around the nucleus. The proton and the neutrons, which are located in the nucleus have the same relative mass of 1, which has been estimated to be about 2,000 times bigger than that of the electron, which has a relative mass of 0.0005. This shows that, the mass of an atom is located primarily in its nucleus. <span />
        
                    
             
        
        
        
The answer is B.
Water in the form of vapor enter the atmosphere. The vapor accumulates in the atmosphere to form clouds. Once the clouds are heavy enough, the water in the form of droplets fall towards land or as rain. It could also be in the form of other precipitation such as snow or hail. As the sun hits the waters in the land, it causes the water to evaporate and the cycle continues.
        
             
        
        
        
Answer:Valves stop blood flowing backwards
Explanation: Valve are flags of tissue that control the direction of the blood in our heart.,it prevent the backwards flow of blood. valves regulate blood from flowing back into the atria.The right and left atrio-ventricular valves prevent blood from flowing backwards into atria. When the ventricle is full,the valve prevent backwards flow of blood.
 
        
             
        
        
        
Answer:
38 ATP
Explanation:
On complete oxidation of one molecule of glucose yields 38 ATP.  Break up of energy production is given below:  
- During glycolysis 2 ATP and 2 NADH is produced.
 - During formation of Acetyl CoA, 2 NADH is produced.  
 - During Citric Acid Cycle, 2 ATP, 6 NADH, 2 FADH₂ are produced.  
 
Finally during Electron transport chain, reduced coenzymes NADH and FADH₂ oxidised to release ATP. Each NADH produce 3ATP and each FADH₂ produces 2 ATP. Altogether 10 NADH is produced during entire process of cellular respiration which yield 30 ATP and 2 FADH₂ yields 4 ATP. Therefore, on complete oxidation of one molecule of glucose yields 38 ATP.