In my opinion, the correct answer among the choice given above is option D. It is advantageous for grazing mammals to gather in groups because groups <span>offer greater protection from predation. It protects them  because predators will think twice in nearing the group because it is outnumbered.</span>
        
                    
             
        
        
        
Answer:
The correct answer will be option-C
Explanation:
Lead is a metal found in the Earth's crust which through human practices like using it in paints and other products cause lead poisoning in humans due to accumulation of lead in the body.
Lead poisoning can affect the child above 6 years and adults and prove harmful as its increased concentration can cause severe health problems common of which are the development of anaemia due to large consumption, brain damage, reduced mental growth and severe stomach ache.
Thus, Option-C is the correct answer.
 
        
             
        
        
        
The answer is; 24 hours.
Scientists called the full rotation of the earth a day and divided it into 24 hours on the clock. This means from sunrise to next sunrise. They also divided the earth into latitudes that indicate time zones. When one point on earth rotates and return to the same position in space, it has lapsed 24 hours. 
 
        
             
        
        
        
Oxygen and glucose are both reactants in the process of cellular respiration. The main product of cellular respiration is ATP; waste products include carbon dioxide and water.