Answer:
The correct answer will be option-C
Explanation:
The rhythm of the heartbeat is controlled by the pacemaker of the heart called the sino-atrial node.
The SA node generates action potentials which trigger the contraction and relaxation of the atrium and ventricles. The membrane potential generation initiates by the depolarization of the cell membrane when the L type of Ca⁺² ions opens up and calcium ions enter the cell.
This depolarizes the cell until the potential threshold is reached which lies between the -40 and -30 mV.
Thus, Option-C is the correct answer.
 
        
             
        
        
        
Answer:
a. amygdala
Explanation:
According to my research on studies conducted by various neurologists, I can say that based on the information provided within the question the part of the brain that was most likely under investigation in this study was the amygdala. This can be said because the amygdala is the part of the brain that is responsible for emotions, survival instincts (which dictates fear levels), and memory. 
I hope this answered your question. If you have any more questions feel free to ask away at Brainly.
 
        
             
        
        
        
Salinity refers to the principal characteristic that determines whether an aquatic ecosystem is classified as marine or freshwater. It is the measure of all the salts dissolved in water.
 
        
                    
             
        
        
        
Answer:
In dividing cells, most of the cell's growth occurs during interphase. 5. The mitotic spindle(s) is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division.