Answer: D) By decreasing the activation energy of a reaction
A catalyst is a substance that speed up the rate of chemical reaction without affecting the product of the reaction. They only affect the rate of reaction not the yield of reaction.
Catalyst provide an alternative reaction pathway that has lower activation energy  than that of uncatalysed reaction. It increases the frequency of collision and because of these greater collision which lowers the activation energy of the reaction.
 
        
                    
             
        
        
        
Carbohydrates
I'm not sure but....Please correct me if I'm wrong!! :)
 
        
             
        
        
        
Answer:
1. it's an atom
Explanation:
An atom is the smallest particle of an element, having the same chemical properties as the bulk element. The first accurate theory explaining the nature of matter was Dalton's Atomic Theory: 1. All matter is composed of atoms, and atoms are indivisible and indestructible.
 
        
             
        
        
        
Geiger-Muller tube is instruments requires you test three times the background of the work area.
<u>Explanation</u>:
These detectors are gas filled detectors and hence requires time for responding to the value. This time is taken because during this period it collects the electric charges and features of the electric circuit. It also gets stabilized during this period. This device has thumb rule i.e one must wait or hold for at the least 3 times the time constant before getting the precise and accurate reading. The time constant order is 10 seconds for the ionization chamber but for the Geiger counter it can vary from seconds to greater than 20 seconds
 
        
             
        
        
        
Artic air is the answer to this