Gravity , Explosion
<u>Explanation:</u>
Nebulae are made of dust and gases—mostly hydrogen and helium. The dust and gases in a nebula are very spread out, but gravity can slowly begin to pull together clumps of dust and gas. As these clumps get bigger and bigger, their gravity gets stronger and stronger.
Eventually, the clump of dust and gas gets so big that it collapses from its own gravity. The collapse causes the material at the center of the cloud to heat up-and this hot core is the beginning of a star.
 
        
                    
             
        
        
        
Natural selection
Bc it is
        
             
        
        
        
Answer:
A 
Explanation:
The The one that is appropriate is A because phytoplankton to fish is like the bacteria that is on the bottom of the floor in the water and the fish could eat that phytoplankton and then your shark and whale could eat the fish and get the phytoplankton so your answer is A
 
        
             
        
        
        
Answer:
Genes that are located on the same chromosome and that tend to be inherited together are called linked genes because the DNA sequence containing the genes is passed along as a unit during meiosis unless they are separated by crossing over.
Explanation:
 
        
                    
             
        
        
        
Answer : cathode, protocathode 
During an electrochemical reaction, electrons move through the external wire toward the cathode and positive ions in the salt bridge move toward the protocathode.