You are presented with the quiz "Many plants go dormant during the  " 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "many plants respond to the days growing shorter in the fall by going dormant" and "after the autumnal equinox, days gradually shorten in the Northern Hemisphere". 

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


 

   autumnal equinox        