If you wanted to encourage a child to eat a healthier diet, at first you might smile or nod when the child was willing to take a small bite of a healthy food item on her plate. Then you might only smile and nod when the child took a full bite of the food. Then you might only response when the child ate several bites, finally only when the child finished the serving on her plate. You are changing this child's behvior through the process of-

Shaping

Explanation:

Shaping refers to promoting patterns that come close to or approximate the desired target behavior.  It process of developing behavior that an individual does not inhibit at present. First developed by the famous psychologist B.F Skinner, the measures involved are also called successive approximations as they follow the desired behavior successively.

what words? are you talking about to complet what sentence

it should be d or b but i'm sure it's d