Answer: elastic fibers
Explanation:
Elastic fibres are the essential durable component present in mammalian connective tissueand functions to provide proper pulmonary,  cardiovascular and intestinal system structure and function. Their structural function is to provide elastic recoil and resilience for the tissues.
Elastin fibers ahve two main including microfibrils and elastin containing fibrillin play a mechanical and structural role in the arteries, and their important function is to provide the tissues with resilience and elasticity. 
Hence, elastic fibers helps arteries to adapt to changes in blood pressures that accompany the heartbeat.
 
        
             
        
        
        
The correct option is C.
Scanning electron microscope is a type of microscope that uses beams of electrons that are reflected to form images to scan the surfaces of mounted biological specimens. High resolution, three dimensional images can be obtained via the reflected beam of electrons. Thus, the electron scanning microscope is the perfect microscope for examining the contours on the surface of a bacterial cell.
        
                    
             
        
        
        
Answer:
The modern medical era began when an absent-minded British scientist named Alexander Fleming returned from vacation to find that one of the petri dishes he forgot to put away was covered in a bacteria-killing mold. He had discovered penicillin, the world's first antibiotic.
 
        
             
        
        
        
Correct Question:
An asynchronous counter signal:
Answer:
overrides the clock-gated input signal(s). 
Explanation:
An asynchronous counter signal normally overrides the clock-gated input signal(s).
An asynchronous counter is a type of counter whereby each flip-flop output serves as the clock input signal for the next flip-flop signals and preset can be used to override the clock-gated input signal(s).