Answer:
The answer is- A). Because it takes tremendous effort to break free from the laws of gravity to exit the Earth's atmosphere.
Explanation: 
I really don't have an explanation. Except that I love science and I actually pay attention in my classes.
  
        
                    
             
        
        
        
Answer:
Each FADH2 yields about 1.5 ATP via oxidative phosphorylation. 
Explanation:
Most of the ATP molecules are produced by oxidative phosphorylation, not by substrate-level phosphorylation. During glycolysis, 2 ATP molecules per glucose are produced by substrate-level phosphorylation. Similarly, Kreb's cycle also yields 2 ATP per glucose by substrate-level phosphorylation. 
For each pair of electrons transferred to O2 from FADH2 via electron transport chain, 4 and 2 protons are pumped from matrix towards the intermembrane space by complex III and complex IV respectively. It generates the proton concentration gradient required to drive the synthesis of 1.5 ATP molecules. Since oxidation of FADH2 is coupled to the phosphorylation of ADP to form ATP, the process is called oxidative phosphorylation.  
 
        
             
        
        
        
The type of microscope of advanced technology that can produce 3D mages of a cell’s surface is an electron microscope. This microscope uses electron signals to project the surfaces of the cells. The difference between a <span>prokaryotic cell and a eukaryotic cell is the presence of the nucleus. The nucleus is the center of all processes of the cell</span>
        
                    
             
        
        
        
Answer:
plants For example, phototropism is the plant's response to stimulus, i.e. sunlight. A plant hormone “auxin” keeps the plant's direction towards the sun by activating the growth in a particular part of a stem. Similarly, gravitropism in plants responds to the stimulus, i.e. gravity
Explanation:
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Immune System is the system that consists of proteins and cells.