Answer:
Tamoxifen is an irreversible, competitive inhibitor.
Explanation:
In order to binds to the active site of the estrogen receptor protein, tamoxifen have to compete with the other chemical compound, and inhibits the estrogen release, so it is a competitive inhibitor. Then, you said that when tamoxifen binds to the receptor,  the protein is permanently deactivated, so it is also irreversible. 
 
        
             
        
        
        
B, turns red litmus paper to blue
        
             
        
        
        
It’s C I think and I’m not sure