________ coined the term operant conditioning

According to Piaget, preschoolers' thinking is

A) flexible. B) rigid. C) abstract. D) nonverbal.

According to the article Deep Roots about fetal precursors of temperament, DiPietro et al. operationally defined fetal movement as:

(a) questionnaire responses from the mothers (b) actocardiograph readings (c) the number of times the fetus woke the mother at night (d) the strength of the fetal muscle contractions