The bell shaped curve indicates polygenic traits. A polygenic trait is controlled by multiple alleles. Hope this makes sense :)
        
             
        
        
        
There is no element with one valence electron and six energy levels. Only two valence electrons and six energy levels.
Answer:
Calcium
Explanation:
A: Calcium is a group 2 element with two valence electrons. Therefore, it is very reactive and gives up electrons in chemical reactions. It is likely to react with an element with six valence electrons that “wants” to gain two electrons. This would be an element in group 6, such as oxygen.
 
        
             
        
        
        
Answer:
nuclear membrane, endoplasmic reticulum, Golgi apparatus, and vesicle
Explanation:
The structures or organelles in internal membrane system in the cell do all production, processing and secretion function together. A prokaryotic cell does not contain any membrane bound organelles but Eukaryotic cells do have. Nuclear membrane has double membrane and golgi-rendoplasmic reticulum and vesicle contain single membrane so all these organelles are membrane bounded.