What percentage of American toddlers were toilet trained by 18 months in 1957?

Which system in the human body maintains health by recognizing and destroying pathogens that produce disease?

a. the endocrine system c. the immune system b. the hormonal system d. the central nervous system

According to psychologists, flashbulb memories are:

a. relatively pure, unanalyzed representations of incoming information b. memories of factual information and knowledge about the world in general c. unrehearsed memories of how to execute complex tasks and behaviors d. rich records of the circumstances that surround emotionally significant and surprising events