The fact that gravity exists as it can be repeatedly tested and verified
When a person has linked a neutral stimulus and an unconditioned stimulus so that now the neutral stimulus triggers the conditioned response, <u>acquisition</u> has occurred.
<u>Explanation:</u>
A trigger that in the beginning causes no specific answer other than attention concentration is understood as "a neutral stimulus". In operant conditioning the neutral stimulus becomes a conditioned stimulus when used in combined way with an unconditioned stimulus.
Now let us say, for instance, you need to take your child to the pediatrician for a shot. The pediatrist hits a buzzer before the shot to call her nurse to come in and help her conduct the vaccine. Here the buzzer's noise is the neutral stimulus, as it generates no reaction from the infant, but the child knows that.
The erosion or disintegration of rocks, building materials, etc., caused by chemical reactions (chiefly with water and substances dissolved in it) rather than by mechanical processes. HOPE THIS HELPS!! :)