Most of us speak in high-pitched voices when speaking to a young child. Which of the following terms best describes this type of speaking?

To infer babies' emotions as accurately as possible, researchers

A) are best off attending to multiple interacting behavioral cues and seeing how they vary across situations believed to elicit different emotions. B) can exclusively rely on analyzing infants' facial patterns to determine the range of emotions they display at different ages. C) are best off asking parents to describe their infants' feelings because infants cannot describe their own feelings. D) must remember that people around the world do not associate photographs of different facial expressions with emotions in the same way.

While the infant's speech becomes increasingly proficient and complex, his or her use of gestures

a. declines. b. continues at a stable level. c. changes in an erratic and unpredictable direction. d. increases.