Well, what's the following?
 
        
             
        
        
        
Swimming?
lifting weights?
walking briskly?
jumping rope?
the answer is lifting weights
if  it two answer need in the blank 
it have to be lifting weights and jumping rope. 
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C experiment because you can do experiments on people by giving them extra sugar to see who they react
        
             
        
        
        
sorry wish i could but lilke is this a test?