Silver? 
Fun FACT : An apple, potato, and onion all taste the same if you eat them with your nose plugged
 
        
                    
             
        
        
        
Answer:
I believe it may be-
1. Series
2. Parallel 
3. Parallel 
4. Series
Explanation:
In a series circuit, electricity only has one path to follow while a parallel circuit has more than one path to follow.
 
        
             
        
        
        
Answer:
b.) Br and Br
Explanation:
A covalent bond occurs when electrons are shared between two atoms causing them to form a bond. 
A "pure" covalent bond refers to a nonpolar covalent bond. In these bonds, the electrons are shared equally between two atoms as a result of the absence of an (or very small) electronegativity difference. The purest covalent bond would therefore be between two atoms of the same electronegativity. Two bromines (Br) have the same electronegativity, thus making it the purest covalent bond.
Polar covalent bonds occur when electrons are shared unequally between two atoms. There is a larger electronegativity difference between the two atoms, but not large enough to classify the bonds as ionic. In this case, a.) and c.) are polar covalent bonds and d.) is an ionic bond.
 
        
             
        
        
        
<span> iron (Fe), ruthenium (Ru), osmium (Os) and hassium (Hs). They are all transition metals.</span>
        
             
        
        
        
D...........................