Answer:
The formation of magnesium chloride, MgCl2, is another example of ionic bonding. When magnesium reacts with chlorine, a magnesium atom loses two electrons and becomes a positively charged ion, Mg2+. At the same time, two chlorine atoms gain one electron each and become negatively charged chloride ions, Cl−.
 
        
             
        
        
        
<span>Physical weathering is a term used in science that refers to the geological process of rocks breaking apart without changing their chemical composition. Over time, movements of the Earth and environment can break apart rock formations, causing physical weathering.</span>
        
             
        
        
        
Bursa - A small sac that lubricates the area around a joint where friction is most likely to occur 
ex. elbow, knee, or shoulder
        
             
        
        
        
The Precambrian time refers to the time 4.5 billion to 542 millions year ago. This period is characterized by having reduced atmosphere and included reduced compounds. Scientists believed that atmosphere at that time was devoid of free oxygen and CO2 was present in excess. Before the complex life evolved on the Earth, the Precambrian Earth's ocean contained dissolved carbon dioxide.
        
                    
             
        
        
        
Sample b is the control group because it’s the group not being tested and being kept the same.