You are presented with the question "Plants detect and respond to what?" and the following answer choices: 
- water cycles
 - Greenhouse gasses
 - plant cycles
 - Electrical energy
 - sleep cycles
 - heat or cold
 - Diurnal cycles
 - Temperature changing

Now knowing that plants detect and respond to the daily cycle of light and darkness and diurnal cycles Diurnal cycles are the daily cycles of light and darkness, choose the best answer.


 

       Diurnal cycles  