Answer:
Ecosystem services. 
Explanation:
Essential services, such as water purification, nutrient cycling, and plant pollination are all examples of Earth's ecosystem services.
An ecosystem can be defined as the natural living habitats of both living and non-living organisms. 
Hence, this essential services that are being provided by the ecosystem are really very vital, important and useful for the sustenance of life, both for humans and enhances social welfare. 
 
        
             
        
        
        
B. Peter the Great on May 27, 1703.
        
             
        
        
        
Answer: D
Explanation:
OLDER WORKERS ARE NOT WILLING TO LEARN NEW SKILLS. 
They also lack sufficient technological skills and are unable to learn new skills.
 
        
                    
             
        
        
        
 Answer:
four years old
Explanation:
Roberta and her peers are most likely four years old. Most children tend to recognize and label stereotypical gender groups at about 2 years of age and at 3 years they are able to recognize their own gender and at age 3 to 4 years they use gender labels quite consistently. However, at age 5 and 6 children become rigid about gender stereotypes and preferences. Roberta and her classmates are likely 4 years of age.