Joseph uses classical conditioning to teach his sister to be afraid of squirrels. To be successful, he must pair the neutral stimulus, the squirrel, with a(n) , such as .

Explanation:

Such type of stimulus that is trigger by the neutral in nature is called a conditioned stimulus such as the sound of the bell and some other. Such type of stimulus that is biologically potent is called an unconditional stimulus such as the taste of food and some other things. When the biologically effective stimulus is used with neutral stimulus then the classical conditions are formed that are used in the learning process.

i think this picture will you.

(nitrogen fixation) will be your answer sorry if im wrong