Answer:
 A. Bubbles formed
Explanation:
When a student added a piece of limestone to a solution of hydrochloric acid, bubbles are formed.
The bubbles are as a result of the CO2 gas that is formed. 
Below is the reaction:
CaCO3+2HCl → CO2+H2O + Ca++ + 2Cl-
From the left hand side, we can see that the reaction is with limestone and hydrochloric acid. Their reaction forms carbon dioxide gas (CO2), water (H2O), dissolved calcium (Ca++) and dissolved chlorine (Cl-) on the right hand side. 
With due observation, bubbles will be seen evolving from the reaction. These bubbles formed is the carbon dioxide gas which reveals that a reaction is taking place.
 
        
             
        
        
        
Answer:
ok i wonder what grade this is because i am not understanding this.
 
        
             
        
        
        
<span>A. My teacher wants me to consider joining the advanced journalism class next spring. 
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Answer:
Espqñol XD no hablo inglés