Answer:
option d is the correct option. all the cell in the embroyo would be capable of attaching to one another regardless of the cell type.
Explanation:
cadherins are molecules that allow cell adhesions. various number of cell bind together using this molecules for 
proper functioning.
 
        
             
        
        
        
Answer:
The stratospheric ozone layer absorbs ultraviolet (UV) radiation, preventing dangerous UV rays from hitting Earth's surface and harming living organisms. UV rays cannot be seen or felt, but they are very powerful and change the chemical structure of molecules.
Explanation:
 
        
                    
             
        
        
        
Answer:
The functions of nucleic acids have to do with the storage and expression of genetic information. Deoxyribonucleic acid (DNA) encodes the information the cell needs to make proteins.
Explanation:
 
        
             
        
        
        
What do you mean <span>It has been observed that certain species of insects which had not previously caused significant harm have become serious pests. the best explanation for this phenomenon is that the pesticide killed off predators which had previously held this species in check. a mutation occurred in the species. the pesticide increased the vigor of the species. was able to be used by the pest as an additional food source is also a reproductive for some insect species. </span><span />
        
             
        
        
        
Answer:
Concentration gradient
Explanation:
Concentration gradient of the ions across the membrane generates the membrane resting potential.
Concentration gradient means that there is unequal distribution of the ions on different sides of membrane. For example, the concentration of K ions is much higher within the cell then out of the cell. Opposite is with the Na ions. When ions move from the area of their higher concentration to the are with the lower concentration, we say they move down the gradient or diffuse (no energy required). On the other hand, movement of ions against their gradient means that this process requires energy and involves protein pumps.