What is the process in which high-frequency sound waves scan the mother's womb to produce an image of the unborn baby, whose size and shape can then be assessed?

An example of motor development research is

A. the comparison of various types of stimuli and their effects on reaction time of college students B. the examination of mass and distributed practice and their effects on the learning of 35-year-old subjects C.the administration of a reaction-time test to 15-year-olds and 25-year-olds and comparing their test performances D. the comparison of the body composition of male and female distance runners

In the early twentieth century, psychologists were inclined to explain motivated behavior by attributing it to:

a) emotions. b) incentives. c) learned responses. d) instincts.