The best word that will complete the description of gold should be luster making the statement into,
        Gold has a shiny, metallic luster.
The term luster describes the general appearance of the substance that is observable only in this reflected lights. 
        
                    
             
        
        
        
The answer to your question is Memory
        
             
        
        
        
Duh. It's algebra. Didn't you know that?! 
        
             
        
        
        
The correct answer should be the endocrine system.
Hormones are secreted by endocrine glands in endocrine systems. Opposite of this would be the exocrine system consisting of exocrine glands.
        
                    
             
        
        
        
Answer: B.  Wave A is louder than Wave B.
Explanation: The loudness of sound is measured in unit called decibels (dB). 
A decibel unit measures the relative intensity of sounds on a scale from zero to about 100 dB. dB is a measure of intensity, which relates to how much energy the pressure wave has. 
Given : Wave A is rated at 100 dB, and Wave B is rated at 90 dB. 
Thus we can infer that as wave A has a higher value than wave B, wave A is more louder than wave B.