Four-year-old Karen can't remember anything of the first few months of her life. This is best explained by the fact that:
a. The trauma of birth interfered with the subsequent formation of memories. b. Most brain cells do not yet exist at the time of birth. c. Experiences shortly after birth are a meaningless blur of darkness and light. d. She lacked language skills for organizing her early life experiences. e. Babies lack the hippocampus in the brain needed for memory development.