The molecular clock is a scientific technique which presents a means of estimating evolutionary rates and timescales using genetic data. It uses mutation rate of biomolecules when two or more life forms diverged to estimate the time. Answer is B. 
        
                    
             
        
        
        
I think the answer is D. A good indicator is the resting heart rate. Exercise strengthen your heart and it makes it more efficient. The resting heart rate shows of the heart is pumping blood normally each time it contracts. Having a normal resting heart rate would mean a healthy heart.
        
             
        
        
        
Answer:
The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. The basic function of the cell membrane is to protect the cell from its surroundings. It consists of the phospholipid bilayer with embedded proteins.
 
        
             
        
        
        
Answer:
D. Some of the bacteria may be resistant and survive.
 
        
             
        
        
        
Answer:
A fall-arrest system should be worn while climbing a tree or any tall structure. This will enable the person to have a thing to break or slow his fall if he loses his grasp from the trunk of the tree.