Research Suggests That We Typically Forget Our Dreams Upon Waking

Research suggests that we typically forget our dreams upon waking because:

A) dreams often arouse anxiety that could intrude into our daily life.
B) they are based on random neural activity forming disjointed images with no meaning.
C) they often are sexual or violent in nature and our conscious mind represses them.
D) cortical neurons that control the initial storage of new memories are turned off during sleep.