Answer:
Structures that have no apparent function and appear to be residual parts from a past ancestor are called vestigial structures. Examples of vestigial structures include the human appendix, the pelvic bone of a snake, and the wings of flightless birds.
Explanation:
please give me brainlist and follow
 
        
                    
             
        
        
        
There are choices for this question namely: 
<span>A) tonsil
B) thymus
C) Peyer's patch
D) appendix
</span>
The correct answer is "tonsil". Tonsils are lymphoid tissue that is found in the oral mucosa. The tonsils are arranged in a ring-like fashion called the Waldeyer's ring. This ring comprises of two tubal tonsils, two palatine tonsils, one adenoid tonsil, and one lingual tonsils. In cases of infection involving the oral mucosa and the pharynx, the tonsils become inflamed as well and the condition is called acute tonsillopharyngitis.
        
             
        
        
        
There numerous of them but some of them would be contaminated soil which can be followed with altered soil chemistry that contains fewer soil organisms that are essential. The third one would be surface runoff due to extensively modified hydrology of the area. 
        
             
        
        
        
Excitation-contraction coupling refers to the series of events that begins with the excitation of the sarcolemma in response to stimulation by a neurotransmitter, and results in the release of calcium ions from the sarcoplasmic reticulum.
Hence, option D is the 1st process that starts the excitation-contraction coupling.