Answer:
I think  its cell membrane
Explanation:
The plasma membrane, or cell membrane, is the phospholipid layer that surrounds the cell and protects it from the outside environment
 
        
             
        
        
        
D. regulates which materials enter and leave the cell
        
             
        
        
        
Answer:
b. ecosystems in a region, species in an ecosystem, and genes and alleles in a species.
Explanation:
Biodiversity has three levels - ecosystem, species and genetic diversity. Therefore, Biodiversity  can be defined as the variability among living organisms involving terrestrial, marine, and other aquatic ecosystems, genes and alleles in a species and their ecological complexes such as diversity within species, and between species of the ecosystems.