You drop it barely above the ground
The answer is biological evolution.
The theory of biological evolution explains how organisms evolved during the time. It explains how the characteristics of different species changed over generations. According to the theory, most of current species developed from some distinctly different species that have lived a long time ago.
The answer is D. phobias. The little Albert experiment demonstrated that emotional responses can be conditioned in human beings. The 9 months boy was exposed to different stimuli which included a rabbit, masks, a white rat, burning newspapers and a monkey. After some time he was exposed to the white rat and later a loud noise of metal was made and it scared the boy. This exposure was repeated and eventually the boy became afraid of white furry things including animals.