Answer:
aquarium light
Explanation:
Unconditioned stimulus -
It refers to the action , smell or any word , that unconditionally initiates the response , is referred to as the unconditioned stimulus .
For example , the smell of food , make the person hungry , here the smell of food acts as an unconditioned stimulus .
Similarly , the lights of the aquarium acts to trigger the fishes about the food and all comes to the top , in order to catch food .
Hence , the correct answer is aquarium light .
