The zygote, a single cell, implants its self to the uterine wall and it developes into an embyro which is a cluster of cells. 
        
             
        
        
        
Microtubules provide a rigid structure, or cytoskeleton
        
                    
             
        
        
        
Answer: Enlarged brain because this is how i found it it was on quizlet
Explanation:
 
        
             
        
        
        
<span>The EPA under the Toxic Substances Control Act also referred to as the TSCA are responsible for setting rules and regulations regarding polychlorinated biphenyl, PCB. Tina should reference the TSCA to help support her protest against the very toxic chemicals and compounds in PCB.</span>