After a quick search, I was able to find a source with your question and its multiple choice answers
Next time, you should include them, it is helpful!
"Which describes the action of a ligand's competitive antagonist?"
-A.) It decreases the amount of ligand required to activate the protein.
-B.) It blocks the binding of the ligand to its binding site and prevents activation of the protein.
-C.) It binds to a different binding site on the protein, altering the protein shape so that a ligand cannot bind.
D.) When present, it increases the binding of a ligand to its receptor.
Your answer would be "B".
