As a rat is taking a drink of green, licorice-flavored water, it receives a painful tail-pinch. The next day it is given a choice between green water and licorice-flavored water. It is likely to drink:

The rat will most likely take more of the licorice flavored water

Explanation:

The rat will take more keen on taking more of the licorice flavored water than green water because it has associated the taste of the green water with painful pinch it received on the tail, causing it to refrain the next time it has a choice.

In behavioral psychology, animals are known to tie their actions to either pleasurable or painful feelings. Naturally, the behavior of every animal is conditioned in such a way that it seeks pleasure and avoids pain.

Once the rat begins to associate the taste or sight of the green water with pain, it abstains.