You are presented with the quiz "What occurs when the muscular walls of blood vessels contract?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "constriction occurs when the muscular walls of blood vessels contract" and "cocaine also tightly squeezes, or constricts, the coronary arteries that feed blood to the heart". 

So, what's the best answer to the question?


 

       tight sqeezing    