The answer is B. Enzymes.
Enzymes are biological catalysts that help cause reactions in your body.
        
             
        
        
        
i speak english . gracias!
        
             
        
        
        
Answer:- 12 km = 12000 m
Solution:- It's a metric unit conversion where we are asked to convert 12 km to m where km stands for kilometer and m stands for meter. 
In metric conversions, kilo means 1000. 
So, 1 km = 1000 m
It means,  we multiply the given km by 1000 to get the answer in m as:
 
= 12000 m
Hence, 12 km = 12000 m.