D. A struggle for existence is apparent.
If a struggle for existence is apparent, natural selection occurs because all of the weak/unfit/unadapted ones die.
        
                    
             
        
        
        
Answer: Mosses retain soil humidity and prevents its degradation, besides are habitat for little invertebrates.
Explanation: Mosses are non-vascular plants (they don't have conductive vessels as xylem and phloem) that live places as tree trunks, rocks, walls and soils. This habitats must be humids because mosses need water for nutrient transport,  because they don't have cuticle (prevents water lost) and for fertilization. Mosses are important for the ecosistems where they live because retain water in the soils thus prevent erosion and  harbor invertebrates as Tardigrades (water bears).
 
        
             
        
        
        
Oh thats pretty simple that is a gastroenterologist
 
        
             
        
        
        
The muscle elevates and/or adducts a region.
        
             
        
        
        
Answer:
The correct answer is ''The scientific study of heredity''
Explanation:
Genetics is a branch of biology that studies how hereditary characters are transmitted from generation to generation and the diversity that exists among living beings. Inheritance is the physical and biological characteristics that we share with our family and that can determine our appearance and our biological characteristics, that is, our phenotype (eye color, skin type, etc.) as well as our internal characteristics. All of this is largely derived from our genetic components, that is, our genotype.