【正确答案】Children’s one-word utterances are called holophrastic sentences．because they can be used to express a concept or prediction that would be as entire sentence in an adult speech．Usually，one-word utterances serve a naming function to refer to familiar people，toys，pets，food and objects in the child’s environment(such as“Mama”，“Papa”etc．)，indicate certain actions and demands(such as“More!”，“Up!”etc．)，or convey emotion(such as “No!”)．